Geostationary orbit (GEO)

At this height, a satellite takes exactly one day to go around the Earth. That matches the speed at which the Earth itself turns, so from the ground the satellite looks like it is floating in one place in the sky. You can simply point an antenna in one direction and leave it.

One satellite can look down on a very wide area at once, so broadcast satellites and weather satellites sit here. The downside is that it is so far away that signals take time to travel. That is why speech on a satellite phone can arrive a little late. For internet that needs quick responses, low orbit satellites are used instead.

Imagine a person standing at the center of a carousel, turning on the spot at the same speed as the carousel. The child riding a horse always appears in the same place to that person. The Earth and a geostationary satellite relate to each other in just that way.

This orbit is the reason the satellite TV dish on a roof always faces the same way. Comparing it with geostationary orbit also helps explain why satellite internet in low orbit needs thousands of satellites.