What is a geostationary statellite? What are the basic requirements for such a satellite?

Explanation

It is that satellite which appears to be at a fixed
position at a definite height to an observer on
earth.
Essential conditions for geostationary satellites
are as follows:
1. A geostationary satellite should be at a height
nearly 36000 km above the equator of earth.
Its period of revolution around the earth
should be the same as that of earth about its
axis i.e. exactly 24 hours.
3. It should revolve in an orbit concentric and
coplaner with the equatorial plane.
4. Its sense of rotation should be the same as
that of the earth about its own axis i.e. from west
to east. Its orbital velocity is nearly 3-1 km/s.