Some satellites, such as weather and GPS satellites, simply go along for the ride once in orbit. They zip around the Earth several times a day and are never in the same location.
Others have to be more precise.
Satellites for TV, communications, and surveillance are created to stay in the same location, above the same spot of the planet, at all times of the day. When they drift a bit, satellite operators have to “drive” them back into the correct spot using propulsion.
Mitchell Walker, an associate professor of engineering at Georgia Tech, explains propulsion–and how more efficient propulsion means cheaper services for you.
Source: Georgia Tech