The URL points to an executable binary file (program) on the Web server (not on the user's client computer).
This program executes on the Web server (not on the user's client computer).
This program can produce output that looks like a Web page and can be interpreted by a browser. This is a virtual Web page that probably doesn't exist on the server.
Any file stored in the cgi-bin directory of the Web server is treated as a CGI program to be executed.
CGI program files on the Web server typically have a .cgi filename extension.