Earth

The third planet from a star named the Sun. The only planet in our solar system whose surface has liquid water, covering over 70% of the surface and dividing it into four oceans and seven continents. There is a relatively thick atmosphere composed of about 2/3 Nitrogen, 1/3 Oxygen, plus trace.

The interior of the Earth is, like the other terrestrial planets, divided into an outer silicaceous solid mantle and an inner nickel-iron core. Our planet is big enough to have the core differentiated into an liquid outer core, which gives rise to a weak magnetic field, and a sold inner core.

The Earth is unusual in having a large, Terrestrial-like Moon that is about 1/4 of the planetary diameter. By coincidence, the moon is just far enough away to have the same apparent angular size as the Sun. Probably the Moon formed from the collision of a Mars-sized planet into the early Earth, which explains for instance its lack of iron.

The Earth is the only known place in the universe that supports life, including intelligent species such as humans and to a lesser extent apes, dolphins, and maybe a few others.