Planet
A Planet is a celestial body in space that normally orbits a star.
Description
The definition of what is constituted a planet varies, but normally planets are considered to: 1) orbit a star, 2) not orbit another celestial body that isn't a star nor be a binary star, 3) not have any other objects (other than a moon) share it's orbital region unless smaller objects were pulled in by it's orbit. There are two types of planets in the galaxy: gas giants and terrestrial (or rocky) planets. The former of the two normally being the largest type of planetary classification.
Planets also host a multitude of atmospheric conditions and sizes.