what is a satellite

Satellite are smaller objects that move around a larger object (planet) in circular/elliptical paths due to (mutual) gravitational interaction between the body (like planet) and the satellite.

Satellites are of two types:

 (1) Natural satellites and (2) Artificial satellites. 

Natural satellites: These are celestial bodies that orbit a planet or a dwarf planet. 

Example: Moon is the natural planet of Earth.

Artificial satellites: Artificial satellites are satellites made by humans and placed into an orbit to revolve around earth or any other planet. 

Example: The first artificial satellite Sputnik 1, was launched by the Soviet Union in 1957.