Here's why:

* Orbital Motion: The Moon orbits the Earth in an elliptical path. This means it's constantly changing direction as it travels around our planet.

* Speed: While its speed is fairly constant, it's not perfectly so. The Moon's speed varies slightly due to the elliptical shape of its orbit.

* Rotation: The Moon also rotates on its axis. This rotation takes about the same amount of time as its orbit around the Earth, which is why we always see the same side of the Moon.

So, the Moon is constantly moving in a complex combination of orbital and rotational motion.