Here's why:

* The sun is the source of light: The sun is a giant ball of hot gas that produces its own light and heat through nuclear fusion.

* The moon reflects light: The moon doesn't produce its own light. We see it because it reflects sunlight.

* The moon's phases: The different phases of the moon (new moon, crescent, full moon, etc.) are caused by the changing angles at which we see the sunlit portion of the moon as it orbits the Earth.

So, while the moon appears to shine, it's simply reflecting the light from the sun.