The Moon's phases are the way the Earth casts a shadow over the Moon. It creates different places that the Moon has light. Like in a first quarter only half the the Moon has a shadow.The other side has light because the earth isn't blocking the Moon on one side from the Sun’s lights. Phases occur every month in every year. The phases of the Moon repeat themselves every month and every year.
The phases of the Moon occur when the earth makes a shadow over the Moon on one certain part.