CGI variables?

I went through a video training program from lynda.com and I am trying to make a simple email form. With each input text field, a variable is to be assigned to it. For example, name = realname email = username

It said that you need to use variable names the CGI will recognize for the fields. Does anyone know what the list of possible names are? The trainging vid said to contact the CGI but they have been little help.