Earth is the third closet planet to the Sun, and takes one year to obit it. Mercury, Venus, Mars and Earth are the only four rocky planets in the solar system. They are also called terrestrial planets.
Generally, terrestrial planets have a similar structure, which is composed with a central metallic core and a surrounding silicate mantle.
The core of earth is a huge mass of iron. Outside the core, there is a layer called mantle that is made from heavier rock. On top of mantle, there is a hard rock crust.


Terrestrial planets possess atmospheres that generated through comet impacts or internal volcanism. The Atmosphere of earth contains oxygen, nitrogen and other gases. 70% of the surface of earth is covered by water, which is why earth looks a like blue from space.
All these makes earth have the right conditions for life, e.g. right temperature, oxygen, water and etc.