What is a geostationary orbit?

Answer

The time it takes for a satellite to revolve around the earth is unambiguously related to the radius of its orbit, which is therefore equal to the radius of the earth + the height of the orbit above the earth’s surface. The larger the radius, the more time the satellite needs.
For low orbits of 150 height, for example, a revolution takes about one and a half hours. So suppose you just let a satellite orbit the earth from west to east, the normal direction, above the equator, at such a height that it takes the satellite 24 hours. Since the Earth itself also rotates eastwards in 24 hours, that satellite will APPEARLY hover over a fixed point above the equator. So it APPEARS to stand still (“stationary”) opposite the earth (“Geo..”). Hence the name geostationary. The height above the earth’s surface that you need for this is 36000 km.
For example, if you want to have a communication satellite between Europe and America, it is best to place it in a geostationary orbit above the equator at a western length halfway between Europe and America. In this way, the satellite will be and remain accessible from both continents at any time.
You also have geosynchronous orbits. These are also orbits with an orbital period of 24 hours, but now ellipsoidal. As a result, you will no longer see the satellite hovering on an APPEARING fixed point from Earth, but will perform a looping movement around a certain point.