* Earth is spinning: Our planet rotates on its axis, completing one full rotation approximately every 24 hours. This rotation is what causes day and night.

* Relative motion: As the Earth spins, it carries us along with it. From our perspective on Earth, it appears as though the moon (and everything else in the sky) is moving across the sky.

* The moon's actual motion: While it appears to move across the sky, the moon is actually moving in its orbit around the Earth. This orbital motion takes about 27.3 days to complete.

In summary: The moon's apparent movement across the sky is a combination of the Earth's rotation and the moon's own orbital motion. We see the moon moving because we are moving along with the rotating Earth.