This visualization shows the Moon's phase at hourly intervals throughout 2021, as viewed from the Northern hemisphere. The Moon always keeps the same face to us, but not exactly the same face. Because of the tilt and shape of its orbit, we see the Moon from slightly different angles over the course of a month. When a month is compressed into 24 seconds, as it is in this animation, our changing view of the Moon makes it look like it's wobbling. This wobble is called libration, from libra, the scale.
Supplemental graphics show the Moon's orbit, subsolar and sub-Earth points and the Moon's distance from Earth at true scale. Craters near the terminator are labeled, as are Apollo landing sites and maria and other albedo features in sunlight.