Here's why:
* The moon orbits the Earth: The moon doesn't have its own light source. Instead, it reflects sunlight that reaches it.
* Lunar phases: The different phases of the moon (new moon, crescent, full moon, etc.) are caused by the changing angles of sunlight reflecting off the moon as it orbits Earth.
So, while the moon doesn't generate its own light, it's bathed in sunlight for about half its orbit around the Earth.