Like cable modems, satellite Internet uses a TV channel to transmit data to the home. Thus, a user dials up the Internet over the phone system as usual and connects via the satellite company's gateway. This monitors users' requests, caches the replies and uplinks them to the satellite to be broadcast at very high speed. Hundreds of replies are transmitted at the same time, each encoded so that only the intended recipient can read them. The system is good for downloading data, ok for browsing but not so good for streamed audio and video, due to the combination of the delay in orbital transfer and the caching at the uplink.
Speeds vary considerably.