Earth is the name of the home planet of the Humans. As such, it is the origin of the alternative name for Humans, Earthlings.
Earth is the third planet in the Sol system, which can be found at Hyperspace coordinates 175.2, 145.0. It is a water world with a single moon. It was slave shielded by the Ur-Quan Kzer-Za after they destroyed the Earth forces in 2134 (or possibly early 2135).