htmls

I have thepic of the file here which I am creating.... The extreme left menu is the list of the items. the top right is the item and bottom right is the description. Now, the trouble is that, I want it such that If I press any thing in MENU, then the description and item both should...

What is CGI script and how it can be helpful in the <form> tag of HTML's I have tried most of the stuff, but that doesn't help.