The four terrestrial planets are known as Mercury, Venus, Earth and Mars, they are all rocky planets composed primarily of silicate rocks and/or metals. They are all the planets closest to the sun in our Solar System. The Gas Giant's or Jovian Planets and are composed mainly of a combination of gases/elements: hydrogen, helium, and water that exist in various physical states. These are Jupiter, Saturn, Uranus and Neptune. Behind them is the dwarf planet Pluto (which has recently been re-instated officially as a planet), this is located in the Kuiper Belt.
