This module is a thorough introduction to CGI and discusses how a CGI program interfaces with the Web server, how it communicates with the Web client or browser.
Some of the concepts introduced in this module are:

1. The GET and POST methods
2. Form data-encoding
3. The query string
4. Form elements, or widgets

When you are done with this module, you should have a good understanding of how Web forms work and how to interact with them using CGI.