If you look up to the sky every night for a week, you see the same moon. But each night it looks a little different.
The moon moves in familiar patterns called phases. The moon is the closest celestial body to the Earth. And also the only celestial body that humans have stepped foot on. As the moon orbits around the Earth, it changes angle between the sun and us. When we see it at different angles, it appears to be a different shape.
The moon has no light of its own. The light we see comes from reflections of the sun's rays. When the moon seems to shrink, we say that is is "waning." When it grows, we say it is "waxing." Some well-known phases include the "full moon," "new moon," and "crescent moon."
With no atmosphere to protect it, the moon is vulnerable to asteroids. Meteorites are responsible for the craters we see on the moon.