In this file, we see the various phases of the Moon over the period of a (synodic) month.
The Moon is in synchronous rotation around the Earth, so it only shows one side of itself to the Earth, although the amount of that side which is illuminated depends on its position relative to the Sun. Hence we see a range of illuminations of that side of the Moon, which we call its phases.
There is no "dark side" of the Moon: the whole Moon is illuminated by the Sun over the course of a month. What used to be erroneously called the dark side of the Moon is just the side we never see here on Earth.
The sequence of illuminations of the Moon is a lunation. The time period for this to occur is a synodic month, or just month, a period of that averages 29.5 days. the time period for the Moon to rotate once with respect to the "fixed" stars is called a sidereal month, and it averages 27.3 days.
The gentle side -to-side rocking motion of the Moon during a lunation is called libration. You can read about it here.