Satelite

A Satelite is any object that revolves around another object in space. This could be a Moon, Planet, or actual mechanical satelite. (like the ones used for GPS')

NASA
NASA has built many mechanical satelites and is in charge of most of them. They built the original GPS for the military, but have since then used it for every person. They also built satelites for weather and other such purposes.

The Moon
The Moon is a well known satelite as it is the only one to revolve around the earth. This may not be surprising on the surface, however this is not the case. Most planets have over three moons or other satelites orbiting it, but for us this is not the case.