Cache: A section of memory or the Hard Drive where data can be stored for rapid or frequent access.

Certificate Authority: An issuer of Security Certificates used in SSL connections.

CGI: (Common Gateway Interface) - A programming language used to convert data gathered from a web page into another form. A CGI program might turn the content of a feedback form into an email message, or search a server's database with user-entered keywords.

cgi-bin: The most common directory to store CGI programs on a web server. The "bin" part of "cgi-bin" is an abbreviation of "binary", dating back to when programs were referred to as "binaries".

ClariNet: A commercial news service dedicated to a wide range of topics that provides tailored news reports via the Internet. You can access ClariNet news within Usenet newsgroups.

Client / Server: Computer technology that separates computers and their users into two categories. When you want information from a computer on the Internet, you are a client. The computer that delivers the information is the server. A server both stores information and makes it available to any authorized client who requests the information.

Cookie: A piece of information (login names, passwords, online "shopping cart" items, user preferences, etc.) sent by a web server to a web browser and saved to the computer. These "cookies" can then be used at a later date to restore the information when the web server is accessed again. Cookies are usually set to expire after a predetermined amount of time.

Compression: Data files available for upload and download are often compressed in order to save space and reduce transfer times. Typical file extensions for compressed files include .zip (DOS/Windows) and .tar (UNIX).

Cyberspace: This term was coined by author William Gibson in his novel Neuromancer. Cyberspace is currently used to describe the whole range of information available through computer networks.