That site you posted answers it. Intranet is a local network, one used in your college, univ or sometimes by your ISP if you are using cable net. You can tell if you are on an intranet if your IP address starts with something like: 10.xxx.xxx.xxx or 192.xxx.xxx.xxx. These are usually used for intranet or otherwise known as LAN.

Intranet site or internet site? I don't think there is such a thing. If somebody on your network makes his computer a webserver, then it's an intranet site .