Why does the moon waxes and wane?

Answer 1

These are just terms that we use to describe the moon's appearance as its month-long lunar day unfolds for us. The phases of the moon are simply the way the moon appears to us as we watch one lunar day pass. As we look at the moon, we can describe its phase changes this way. When the moon is new and before it reaches half-lit, it is 'waxing crescent'; it's getting bigger, and it's still shaped like a crescent. After the half-illumination point, it is waxing gibbous; it's getting bigger, and it's beyond the crescent stage. After the full moon and before it reaches half-lit, it is waning gibbous, and after that it is waning crescent.

Answer 2

The Moon has no light of its own, and the only reason we can see it is reflected light from the Sun. When the Earth gets between the Sun and the Moon part of the Moon disc will become invisible on account of being in the Earth's shadow.

Answer 3

The moon waxes and wanes due to its position relative to the Earth and the Sun. When the moon is between the Earth and the Sun, we see a New Moon as the dark side faces us. As it moves to the side, we see a waxing crescent, First Quarter, waxing gibbous phases until reaching a Full Moon. It then goes through waning phases until returning to a New Moon.