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.
The phase of the moon is how much of the moon appears to us on Earth to be lit up by the sun. Half of the moon is always lit up by the sun, except during an eclipse, but we only see a portion that's lit up. This is the phase of the moon. Around once per month, every 29.53 days to be exact, the moon orbits around the Earth. As the moon circles the Earth, we can only see a portion of the lit up side. When we can see 100% of the lit up side, this is a full moon.