What causes the moon to shine?

The Moon shines because its surface reflects sunlight.

The Moon does not produce visible light through nuclear fusion or an internal glow. Sunlight strikes its rocky, dusty surface and scatters back into space, where some of that reflected light reaches Earth. The Moon appears bright because it is relatively close to us, even though its surface reflects only a small fraction of the light that hits it.

The changing phases of the Moon are caused by our viewing angle. As the Moon orbits Earth, we see different portions of its sunlit half, creating the new, crescent, quarter, gibbous, and full phases. A full Moon is not actually producing more light; we are simply seeing nearly all of its illuminated side facing us.

A related phenomenon is earthshine. During a thin crescent Moon, sunlight reflected from Earth can faintly illuminate the darker lunar portion. This can make the Moon seem to glow on its own, but earthshine is still reflected sunlight. The Sun is the only naturally luminous object in this basic Earth-Moon lighting explanation.