Here's the breakdown:

* The Sun is the light source. It illuminates the Moon.

* The Moon reflects sunlight. We see the Moon because it reflects the Sun's light.

* The Moon orbits the Earth. As it orbits, the angle at which we see the illuminated part of the Moon changes.

Imagine holding a ball in your hand and shining a flashlight on it.

* Full Moon: When the Sun, Earth, and Moon are aligned, the entire illuminated half of the Moon faces Earth.

* New Moon: When the Moon is between the Earth and the Sun, the illuminated side of the Moon faces away from Earth, so we see a dark, "new" Moon.

* Crescent, Quarter, and Gibbous Phases: As the Moon orbits, the angle between the Sun, Earth, and Moon changes, showing us different portions of the illuminated side.

In summary: The Moon's phases are due to the changing angles of sunlight reflection, not shadows.