Here's why:

* New Moon: During this phase, the moon is positioned between the Earth and the Sun. Its sunlit side faces away from us, making it invisible from Earth.

* Waxing Crescent: As the moon moves away from the sun, a sliver of its sunlit side becomes visible, forming a crescent shape.

* First Quarter: Half of the moon's surface is illuminated, creating a half-circle shape.

* Waxing Gibbous: More than half of the moon is illuminated, becoming more rounded.

* Full Moon: The moon is completely illuminated and appears as a full circle.

* Waning Gibbous: The illuminated portion of the moon starts to decrease, moving back towards a rounded shape.

* Last Quarter: Half of the moon's surface is illuminated again, but the opposite side from the First Quarter.

* Waning Crescent: The illuminated portion continues to shrink, forming a crescent shape again, until it becomes invisible during the New Moon phase.