A satellite works by receiving a signal from Earth and sending the signal back to the Earth. The signal that bounces off the satellite is made stronger before traveling back to the Earth. People on Earth send signals to and receive signals from the satellite using antennas on the ground.
The antennas located on the ground that send and receive signals are called earth stations. These earth stations are placed in various locations around the world. The area served by the satellite depends on the range of the earth station. The signals that travel from the antenna, or earth station, up to the satellite are called uplinks. The signals that travel from the satellite back down to the Earth are called downlinks.
In most cases, the uplink station sends a signal up to the satellite that contains video or audio programming. After receiving the signal, the satellite makes the signal stronger and send it back down to Earth for users to access all over the world. These links are called feeder links.
Satellites are controlled on Earth via uplink stations called control links. Information regarding performance and satellite function is also sent from the satellite back down to the earth stations.