The phases of the Moon are the different ways the Moon looks from Earth over about a month. As the Moon orbits around the Earth, the half of the Moon that faces the Sun will be lit up. The different shapes of the lit portion of the Moon that can be seen from Earth are known as phases of the Moon. Each phase repeats itself every 29.5 days. The same half of the Moon always faces the Earth, because of tidal locking. So the phases will always occur over the same half of the Moon’s surface.