Geostationary orbit
A geostationary orbit is a circular orbit in the equatorial plane, any point on which revolves about the Earth in the same direction and with the same period as the Earth's rotation.
A geostationary orbit is an orbit in which a satellite is always in the same position (appears stationary) with respect to the rotating Earth. The satellite travels around the Earth in the same direction, at an altitude of approximately 35,790 km (22,240 statute miles) because that produces an orbital period equal to the period of rotation of the Earth (actually 23 hours, 56 minutes, 04.09 seconds- Not exactly the length of a day as that is determined both by the Earth's orbit around the sun and the rotation of the Earth itself.).
A worldwide network of operational geostationary meteorological satellites provides visible and infrared images of Earth's surface and atmosphere. The satellite systems include the U.S. GOES, METEOSAT(launched by the European Space Agency and operated by the European Weather Satellite Organization-EUMETSAT), the Japanese GMS and most commercial, telecommunications satellites.
Note: An object in a geostationary orbit will remain directly above a fixed point on the equator at a distance of approximately 42,164 km from the center of the Earth, i.e. , approximately 35,787 km above mean sea level.
A statite, a type of satellite which uses a solar sail to modify its orbit, can theoretically hold itself in a geostationary orbit with different altitude and/or inclination from the "traditional" equatorial geostationary orbit.
Source: from Federal Standard 1037C and from MIL-STD-188
