CGI with rails...

Hi, I'm a newbie to rails and programming... I don't know anything about CGI scripts... The only thing I know about CGI is that it stands for Common Gateway Interface. To be honest with you, this is as concrete as it gets!!!!! Please someone help me with that so at least I understand what it is, concretely, and that I can use it if I need to. If you guys have examples (code) that might help as well.

Thank you