Whal are Geostationary Satellites? What are their uses?

A geostationary satellite

What are geostationary satellites? What are the necessary conditions for a satellite to appear stationary ?

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

A geostationary satellite is one

Why are geostationary satellites not useful for studies for polar regions? OR Explain the following statement. A geostationary satellite is not useful in the study of polar regions.