What is CGI?

CGI stands for Common Gateway Interface. CGI extends the capabilities of a Web server so that your website can communicate with another script or application.

CGI programs are the most common way for Web servers to interact dynamically with users. Many HTML pages that contain forms, for example, use a CGI program to process the data from the form.

Our CGI service supports server-side includes, form handlers, and hit counters.

or more information, see:
Which programming languages do you support with CGI?
Where do I upload my CGI scripts and applications?