Here's why:

* The moon's phases are caused by the changing angles of sunlight reflecting off the moon's surface as it orbits the Earth. As the moon orbits, the amount of the sunlit side that we see from Earth changes.

* Earth's shadow causes a lunar eclipse, not the moon's phases. A lunar eclipse occurs when the Earth passes directly between the sun and the moon, casting its shadow on the moon.

Here's a simple analogy: Imagine a ball being lit by a lamp. As you move the ball around the lamp, the amount of the ball's surface that is illuminated changes. The same principle applies to the moon and the sun.