Account-Level Filter: A rule that determines where email, delivered to a domain's main email account and meeting certain criteria, will be delivered. See also Filter.

Addon Domain: An additional domain name associated with your cPanel account. Each addon domain is stored in its own directory which you can configure. This allows you to manage multiple domains from a single cPanel account. Addon domains must be registered with a domain name registrar to work.

Analog: A program that provides information about the visitors to your website in both graphical and statistical views. More information about Analog can be found at its website: http://www.analog.cx/.

Anonymous FTP: A process whereby visitors without FTP accounts may upload and download files to and from your site. Although it poses security risks, anonymous FTP can be convenient if you wish to make files publicly available for downloading. When setting up anonymous FTP, it is important to protect any sensitive information by changing file permissions and directory access permissions.

Apache: A program that receives requests from web browsers. It then responds by “serving” web pages to the browsers; for this reason, it’s called web server software.

Apache Handler: A means of telling the Apache software how to process a given type of file. By default, Apache only handles certain file types; using cPanel, you can configure Apache handlers for other file types. For more information, see Apache's handler documentation.

Authentication: A process for confirming the identity of someone with whom you want to share sensitive information. On the web, authentication usually involves either a username and password set or a public/private key pair.

Auto Responder: A feature of cPanel that allows you to set up automated replies to incoming email. This feature can be useful for confirming the receipt of mail, or for informing correspondents that the recipient is unavailable (for example, while on vacation).

AWStats (Advanced Web Statistics): A program that provides information about the visitors to your website in both graphical and statistical views. More information about AWStats can be found at its website: http://awstats.sourceforge.net/.

Backscatter: Bounce email messages (or failed Delivery Status Notifications) erroneously sent to a domain whose name has been forged as the sender of spam. Using SPF on your mail server should reduce backscatter.

Backup: A copy of your website’s files, directories, databases, and email configurations. Keeping a backup copy of your website on your personal computer is a wise precaution.

Bandwidth: The amount of data transferred to and from a web server. Every time a visitor views a file (whether it’s a web page, image, video, or audio file), that file has to be transferred to the visitor’s computer. Bandwidth is the total size of all these files transferred to your visitors’ computers. It is important to keep track of bandwidth usage, as it is limited by web hosts.

Banners: Images which appear on a website, often as advertisements at the top or bottom of a page. Often, banners alternate with each successive visit to the page.

BoxTrapper: An application included with cPanel that filters spam by requiring would-be senders to reply to a verification email (also known as challenge-response verification). Only after the sender is verified through the reply will his or her original email be accepted.

BoxTrapper Blacklist: A list of email addresses from which incoming mail will be automatically blocked. cPanel automatically sends a configurable warning message upon receipt of mail from a blacklisted address. See also BoxTrapper Ignore List and Whitelist.

BoxTrapper Ignore List: A list of email addresses from which incoming mail will be blocked. cPanel does not send a warning message upon receipt of mail from an ignored address. See also BoxTrapper Blacklist and Whitelist.

BoxTrapper Whitelist: A list of email addresses from which incoming mail will automatically be accepted. See also BoxTrapper Ignore List and Blacklist.

Build: A minor version of cPanel. Builds exist in four types which are, in order from least to most stable, EDGE, CURRENT, RELEASE, and STABLE. Please visit our installation documentation for an in-depth look at each build type.

Catch-All Address: The email address to which cPanel routes any email message sent to email accounts which do not exist at your domain. Also called a Default Address.

CGI (Common Gateway Interface): A protocol that lets a web server communicate with scripts and other software. cPanel’s CGI Center provides an array of CGI scripts that let you generate and manage useful features for your website, including a guestbook, clock, hit counter, countdown clock, and banner ads.

CIDR (Classless Inter-Domain Routing): A routing method that assigns each Internet user to a four-part IP address, with each part separated by a decimal, followed by a slash and a number between 0 and 32.

CLI (Command Line Interface): A means of communicating with a computer by typing commands. On Unix systems, this is also often called a shell.

Client: Any application that accesses a service on another computer. Web browsers such as Internet Explorer can be called web clients. FTP clients include FileZilla and Cyberduck.

cPAddons: Pieces of software that you can install on your website through cPanel. cPAddons provide useful tools to your website. Common examples include bulletin boards, chat programs, and online shopping carts.

CPAN (Comprehensive Perl Archive Network): The main repository of Perl modules, pieces of Perl software. The CPAN library (located at http://www.cpan.org) contains over 12,000 modules, most of which are free of charge. cPanel allows you to search CPAN and install Perl modules.

Cron Job: A command on a server, executed at regular intervals. These commands are stored in a Unix configuration file called crontab.

CSR (Certificate Signing Request): A request, which you send to a certificate authority, for an identity certificate. cPanel can generate a CSR for you, but since authorities vary with regard to the information they require, you should check their requirements before applying for a certificate.

Default Address: The email address to which cPanel routes any email message sent to email accounts which do not exist at your domain. Also called a Catch-All Address.

Directory (Folder): A repository for files, analogous to a file folder on your personal computer. In website management, a directory will contain your web files.

DNS (Domain Name System): The component of the Internet which acts as a “phone book,” converting human-readable domain names (such as www.example.com) into computer-readable IP addresses (such as 208.77.188.166, in the case of example.com).

Domain: The name you give your website, which will appear in your website’s URL and email addresses. Usually seen as example.com, where "example" is meant for your domain’s name.

DomainKeys: An email authentication method that attempts to verify that a message actually came from the domain it appears to have come from.

DSA (Digital Signature Algorithm): A method of generating public and private keys for encrypting data. This algorithm was developed by the U.S. government.

Entropy Banner Manager: A script, included with cPanel, that lets you manage rotating banner images on your website.

Entropy Search: A script, included with cPanel, that creates a search engine for your website.

Error Pages: These pages display warning messages when visitors encounter problems while trying to access your site. cPanel lets you configure the error messages that display for your site. For an in-depth look at HTTP error codes, please visit our HTTP error codes documentation.

Filter: In cPanel, a tool that processes mail according to your preferences. For example, a filter can automatically discard spam or save mail from a specified sender to its own folder. In cPanel, filters can be applied to the main email account on a domain (Account Level Filters), or customized for each individual account (User Level Filters).

Forwarder: A tool that lets you forward a copy of every email message you receive to another address. When a forwarder is set up, you will still receive mail at the original recipient address. If, however, you create a forwarder without first creating the original address, messages will be forwarded to the end address without being sent to the original address, as it does not exist.

FrontPage®: A Microsoft® application that allows you to edit your web page in WYSIWYG (what-you-see-is-what-you-get) format, rather than using HTML code. cPanel provides FrontPage extensions, so you can publish your site using FrontPage, allowing you to skip the FTP process. Newer versions of FrontPage allow you to publish your site using FTP or WebDAV. See the FrontPage User Manual for more information about publishing.

FTP (File Transfer Protocol): A method of transferring files from one computer to another. cPanel comes equipped with an FTP server that can be configured to your preference. An FTP client must be installed on your computer in order to send files to and receive files from the FTP server. Some FTP clients include FileZilla (for Windows®, Linux, and Unix), and Cyberduck (for Mac®).

FQDN (Fully Qualified Domain Name): A name that uniquely defines a domain’s location. It is usually seen as host.example.com. with a trailing dot. For the purposes of cPanel, including a final dot is not necessary, but the domain name must contain at least 2 dots.

GnuPG (GNU Privacy Guard): Free encryption software that lets you generate a matching public and private key. These keys are useful for keeping files private during transfer.

gzip: A program which compresses files for quick transfer. The compressed files use the filename extension .gz.

Home Directory: Your cPanel account’s highest-level directory, which contains all the files and directories used by websites managed through your account. Files placed in your home directory are not viewable online unless they reside in the public_html directory or a subdirectory of public_html.

HotLink: Also known as an “inline link.” A hotlink is a direct link that embeds a file (such as an image or video) from your site into another website. When another site embeds your files, it is using your bandwidth to serve those files.

.htaccess: A file that resides in a specific directory, and contains configuration information applying to all the information in that directory. The .htaccess file may also contain authentication instructions.

HTML (Hypertext Markup Language): The language in which most pages on the World Wide Web are written.

.htpasswd: A file that resides in a specific directory, along with an .htaccess file. The .htpasswd file contains encrypted password information when authentication has been set up for the directory.

HTTP (Hyptertext Transfer Protocol): The method (protocol) for transferring data over the Internet.

IMAP (Internet Message Access Protocol): Along with POP3, one of the two most widely used email transfer methods. IMAP synchronizes email account information with the mail server on a regular basis. If you log in to multiple computers to check your email, IMAP will allow you to see what messages you have viewed, replied to, forwarded, etc. POP3 does not allow you to see this information.

Index Page: The page viewed by default when a visitor accesses a directory of your website. If no index page exists for the specified directory, the visitor will see a list of files in that directory, unless you turn off indexing in cPanel. This page is typically index.html, index.htm or index.php.

IP (Internet Protocol) Address: A number that identifies a computer on a network, making it possible for other computers to find and communicate with it.

Java: A computer programming language used by many web applications. cPanel uses the Java language to provide the SSHTerm and Java Telnet features. These small applications, which run within the context of a web browser, are called applets.

Key: In cryptography, a key is used to encrypt or decrypt information. Keys are an important part of encryption and security and should be guarded appropriately.

Leech: A visitor who uses another person’s password to access a restricted area of a website. cPanel allows you to prevent leeching by redirecting likely offenders or disabling accounts whose passwords have been compromised.

Legacy: A term for an old software program or computer system that is still in use.

Local Host: An easy way to refer to the computer that you are currently working on.

Log: A file, automatically created by the server, that records activities performed by or on the server. For instance, error logs are lists of errors that visitors have encountered on your site.

Mailing List: A list of email addresses which list members can use to communicate. Alternatively, such a list can be used to send email messages to a large group of people. cPanel uses a program called Mailman for mailing list software; for more information, please see its website, http://www.list.org.

MIME (Multipurpose Internet Mail Extensions) Type: Now called an Internet media type, this component of a file identifies the file type, so that web browsers know how to handle it. cPanel lets you specify which application should be used to open files with a given extension.

MX (Mail eXchanger) Entry: A record that specifies where email should be sent for a domain. If you are using an email scanning service or custom mail delivery, you may need to change the MX record for your domain.

MySQL: This term refers to a database management tool, as well as the type of database it manages. Such databases are integral to applications like bulletin boards and retail shopping. cPanel provides an integrated MySQL interface as well as a MySQL database editing tool called phpMyAdmin.

Nameserver: A computer that contains a list of domain names and their corresponding IP addresses. These computers are spread through the Internet and allow you to find where a domain is located. Nameservers gather data about domains over time; therefore, changes to DNS records can take up to a week to reach all the nameservers on the Internet (or “propagate”).

Parked Domain: A second domain that points to your primary domain. When users attempt to access the parked domain, they will see your main website. For example, both http://www.cpanel.net and http://www.cpanel.com go to the same place, as cpanel.com is a parked domain for cpanel.net.

PEAR (PHP Extension and Application Repository): A repository of PHP code. cPanel allows you to search for and install PEAR packages consisting of PHP programs which can perform useful functions for your website.

Perl: Known for its ability to process text, Perl is a useful language for web applications. Perl applications are commonly found as .pl, .pm, and .cgi files and may require Perl modules. Perl modules can be installed within cPanel.

Perl Module: A piece of software written in the Perl language. Modules are common pieces of software that are reused often. For example, rather than writing a set of functions to display calendars, you can simply use a calendar module.

PHP: A computer scripting language in which many web-based applications are written. PHP applications are commonly found with the filename extensions .php, .php4, or .php5. Some PHP applications require PEAR packages, which can be installed in cPanel through the PHP PEAR Packages feature.

PHP Package: A piece of software written in the PHP language.

phpMyAdmin: A graphical application that allows you to manipulate and manage MySQL databases over the Internet. Full documentation for phpMyAdmin can be found at its creators’ website: http://www.phpmyadmin.net.

POP3 (Post Office Protocol version 3): Along with IMAP, one of the two most widely used email transfer methods. POP3 simply copies every message in your email account to your local computer. No information is sent back to your email account about message replies, forwarding, etc. If you use multiple computers to check your email, it is advised that you use IMAP instead of POP3.

POSIX (Portable Operating System Interface): A standardized collection of commands for the Unix operating system.

Private Key: A string of characters that a computer uses to encode or decode encrypted messages it receives. Encryption schemes use a matching pair of keys (one public, one private) to create a secret code so that anyone looking at messages sent from or received by your computer will be unable to determine the contents of those messages without access to the private key. A private key is integral to protecting your confidential information and should be safeguarded appropriately.

Proxy: In computing, a computer or program that serves as an intermediary between two other entities. For instance, a proxy server receives a request from a client, finds the requested resource, and returns it to the client. You can use the cPanel Proxy to access to your cPanel interface when normal access is blocked (for example, from behind a firewall).

Public Key: A string of characters that a computer uses to encode or decode encrypted messages it receives. A public key is provided to anyone you wish to send sensitive information to. Typically, a public key will be placed on a server so you can access that server with encryption.

public_ftp: The subdirectory, located inside your home directory, that holds files available for public download. This is the default directory users will access when they connect to your site via anonymous FTP.

public_html: The subdirectory, located inside your home directory, that holds the files that make up your website. The www directory is a link to public_html. Any files and folders inside of public_html are visible over the Internet, unless you specifically protect them with password protection or using a .htaccess file.

Redirect: A feature that allows you to send visitors who try to access one URL to another URL. cPanel allows you to set up either temporary or permanent redirects. Redirects are useful when you change the URL of a page on your website. You can put up a redirect at the old URL to make sure your visitors are automatically sent to the new URL.

Referer: A web page which links to your site; also called an “HTTP referer.” This spelling is the industry standard term, though it is based on a misspelling of “referrer.”

Root: Specific to Unix and Unix-based systems, a computer account, used by a system administrator, which carries full privileges for configuring a computer system. Also called “superuser.”

RSA: An algorithm for generating public and private keys when sending encrypted data between a local machine and a remote machine. The name of this method is not an abbreviation; it is named after its three inventors.

SCP (Secure Copy Protocol): A method of transferring encrypted files from one computer to another. This method prevents data from being intercepted and read.

Shell: Software that allows you to interact with a computer. Many Unix shells allow you to type commands, and are often referred to as CLIs, or command line interfaces.

Shortcut: A link to an application which allows you to access it from a convenient location, like your computer’s desktop.

Spam: Chiefly, unsolicited email sent in bulk, usually by an automated system. As spam is considered a costly nuisance to the recipient, cPanel includes features like SpamAssassin and BoxTrapper that can cut down on the amount of spam received.

SpamAssassin: An application which can filter suspected spam before you receive it. SpamAssassin can be configured to filter spam more or less aggressively, according to your needs. Learn more about SpamAssassin at its website: http://spamassassin.apache.org/.

SPF (Sender Policy Framework): A feature that allows a recipient server to verify that an email message has really been sent from the domain specified in the From: field. Enabling SPF can prevent your server from receiving replies to spam that has forged your domain name as part of the sender’s address. SPF only works if both the sending and receiving mail servers have SPF enabled.

Spoofing: In email, this term is used to describe the forgery of a domain name as the sender in the header of an email. Enabling SPF makes it more difficult for spammers to spoof your domain.

SSH (Secure Shell Handler): A network protocol that allows a user to log into a remote machine user account securely. cPanel can create keys for authenticating your identity during SSH login, and provides a Java applet for accessing SSH through your web browser.

SSL Certificate: An electronic document (using the filename extension .crt) which binds a public key to an identity consisting of an email address, company, and location. This electronic document is a key piece in an authentication process.

SSL (Secure Sockets Layer)/TLS (Transport Layer Security): TLS is simply the more recent version of SSL. Both are cryptographic schemes that allow for secure interaction between a web browser and a web server. All sensitive data (credit card numbers, login information, etc) that is transmitted over the internet should be protected by SSL/TLS. You can install an SSL certificate on your web site to allow your site to be protected by SSL/TLS.

Subdomain: A subsection of your website that exists as a subdirectory in your home folder. If your domain were example.com, then the subdomain URL would appear as subdomain.example.com.

Tar: Originally derived from “Tape Archive,”a program that collates files for transfer or distribution. Files processed by this program are usually compressed, commonly called “tarballs,” and use the filename extension .tar. Due to the compression commonly used, .tar often precedes the .gz file extension.

Tarball: A file collated by the tar program, and usually compressed.

Telnet: A network protocol that allows a user to log into a remote machine user account remotely. Telnet is similar to SSH, but less secure. Telnet should not be used to connect to your web site except for testing purposes. Login information is sent through Telnet as plain text and can be easily intercepted.

Thumbnail: A version of an image file that is reduced in size, allowing for easy viewing of multiple images. cPanel includes a Thumbnailer tool as part of its Image Manager section.

Thumbnailer: A cPanel tool that automatically sizes down all the images in a directory. The new thumbnails are stored in a subdirectory named */Thumbnails, where * is meant to represent the parent directory containing the original images.

URI (Universal Resource Identifier): On the web, a URI is a string of characters that identifies a website. URI is often used synonymously with the terms “URL” and “web address,” although there are technical differences among the three.

URL (Universal Resource Locator): On the web, a URL is a string of characters that identifies the location of a website. Since IP addresses are difficult to remember, URLs are used instead. For example, it is much easier to remember to go to http://www.example.com than http://208.77.188.166. URL is often used synonymously with the terms “URI” and “web address,” although there are technical differences among the 3.

User: A person who uses a computer to accomplish some purpose.

Visitor: A person who views your website.

Web Browser: An application used to view and interact with sites and pages on the World Wide Web. Examples include Firefox®, Internet Explorer®, and Safari®.

Web Disk: A feature of cPanel that lets you manipulate your web files by dragging and dropping, just as you do on your local computer’s operating system.

Web Root: The top-most directory of your website (namely, public_html or www), inside which all of the files and subdirectories for your website reside.

Web Server: A program, such as Apache, which receives requests from clients (web browsers), retrieves the requested web pages, and “serves” them to the clients.

Webalizer, The: A program that displays various statistics for your website using tables and graphs. Full documentation for The Webalizer can be found at its creators’ website: http://www.webalizer.com.

Webmail: Any application which allows you to access your email through a web browser. The main advantage to webmail is the ability to access your email account from any computer connected to the Internet without having to install or configure a specific mail program.

WHM (WebHost Manager®): Companion software to cPanel, designed for web hosts.

www: For the purposes of cPanel, www is a link to the directory that holds the files that make up your website (/public_html).