The earth and seven other planets together orbit the sun. From the center outwards they are called: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Until 2006 Pluto was a ninth planet, but he was then downgraded to a dwarf planet.
The inner four planets, Mercury, Venus, Earth and Mars are terrestrial planets. They are made of solid, rocky material and their portion of gas (the atmosphere) is very small compared to their total mass. In contrast, Jupiter, Saturn, Uranus and Neptune are largely gaseous. It is assumed that they posses a small solid core. Due to their big sizes they are also called gas giants.
Every single one of these planets represents its own fascinating world which can be explored by space probes and, in the case of the earth, even by foot.