The phases of the moon refer to the different appearances of the moon as it orbits the Earth. This cycle takes about 29.5 days and includes several distinct stages: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. Each phase is determined by the position of the moon, Earth, and sun. During the new moon, the moon is between the Earth and the sun, making it invisible from Earth. As it moves, more of its illuminated side becomes visible, leading to the full moon when the entire face is lit. After the full moon, the visible portion decreases until it returns to the new moon phase, completing the cycle.