Interaction : Common Gateway Interface (CGI)

Why ?

Need for dynamic Web sites

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.