Here's why:
* The moon is a large, rocky body that orbits the Earth. It does not have its own source of light like a star.
* Sunlight shines on the moon's surface. Some of that sunlight is absorbed by the moon's surface, and some is reflected back into space.
* The reflected sunlight is what we see as moonlight. The amount of light we see depends on the angle of the sun, the moon's position in its orbit, and the composition of the moon's surface.
So, the moon is essentially a giant mirror reflecting the sun's light!