CGI

Common Gateway Interface or CGI is a set of rules that describe how a Web Server communicates with another piece of software on the same machine, and how the other piece of software (the “CGI programme”) communicates with the web server. Any piece of software can be a CGI programme if it handles input and output according to the CGI standard.

Usually, a CGI programme is a small program that takes data from a web server and puts the content of a form into an e-mail message, or turns the data into a database query or something of the like. You can often see that a CGI program is being used by seeing “cgi-bin” in a URL, but not always.