The Moon is Earth's only natural satellite, and is lighted by reflecting the light of the Sun, creating phases as the sun shines on different portions of it.
It has a diameter of 3 474 km, around 1/4 the size of Earth and a gravity about 1/6 the amount of Earths.
The moon has two main regions: dark (maria, latin for seas) and light: anorthosite. The dark regions are craters caused by impact from interplanetary debris. The light regions are the valleys of the moon, relatively unscathed.
It has no atmosphere, causing temperature to go between extremes.