Time-lapse a month of moons and the Moon appears to nod, rock and pulse. We call it libration, and it's how we see 59% of the surface.

The Moon's spin is steady but its orbital speed isn't, because the orbit is an ellipse, so it runs slightly ahead or behind, letting us peek around each limb in turn. Add a tilt and our own change in viewing angle and the Moon appears to wobble on two axes while visibly changing size.