What are the phases of the Moon?
Quick Answer: The Moon has eight phases over its roughly 29.5-day cycle: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter and Waning Crescent.
The phases happen because of the changing angle between the Sun, the Moon and Earth as the Moon orbits us. We always see the half of the Moon lit by the Sun, but how much of that lit side faces Earth changes from night to night. This is not caused by Earth's shadow falling on the Moon.
"Waxing" means the lit portion is growing, while "waning" means it is shrinking. "Crescent" describes a sliver that is less than half lit, and "gibbous" describes a shape that is more than half lit. The cycle runs from the dark New Moon, builds to the fully lit Full Moon, then fades back to New Moon to begin again.