hi does anyone know what a cgi-bin is..?

it's a folder to where you place all of your cgi scripts. some hosts allow (i forget the term) "out of bin" cgi scripts. Meaning, scripts can be executed from a different folder other than cgi-bin.

do you make your own cgi-bin or do you already have a cgi-bin on your computer..?

it's usually found on a web host. If you don't have a cgi-bin on your host, either make one (by creating a folder) or your host doesn't support it. Some common hosts, angelfire, geo, etc. doesn't support CGI.