update of the information on the web site required "on the fly" (i.e. dynamically)
e.g. News, Meteorology
need some real interaction with the user : dealing with the forms filled in by
the user
e.g. the basic one : a search engine
CGI is a standard specifying a means for external programs to interface with
information servers
When the web server runs a CGI program, it collects the program's output and
returns it to the web browser. Thus, the browser receives information which
has been dynamically generated.