What is the origin of 'sleep tight'? One of the mysteries of the English language finally explained.
The moon doesn't glow in a very real sense. It reflects the Sun's light. (Or the Earth's light if you're not on Earth and in the right position.) As Quora User says, the moon has a high albedo. So it reflects pretty well.
One half of the moon is always illuminated by the sun. But here on Earth, we can't always see the half of the moon that's lit up. What we call the phases of the moon represent the different fractions of the moon's lighted half that we can see as the moon circles the Earth. [See this infographic on Moon Phases] When the moon and the sun are on opposite sides of the Earth, we perceive the moon as full.