Here's why:

* The Moon doesn't produce its own light. We see the Moon because sunlight reflects off its surface.

* The Moon orbits the Earth. As it orbits, the angle at which sunlight hits the Moon changes from our perspective on Earth.

* This changing angle of sunlight creates the different phases we see: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, Waning Crescent.

So, the different views of the Moon are actually phases in its illuminated surface as seen from Earth!