What is a planet?

A planet must have a number of conditions. 
First of all it has to be in orbit around a star, it must be large enough to make it round, it must be cleared and at last it must not be a satellite. 

Inner planets

The inner planets are those planets that are nearest to the sun: Mercury, Venus, Earth and Mars. 

Outer planets

The outer planets, unlike the inner planets are the further, wich are: Jupiter, Saturn, Uranus and Neptune.