The squat is a very basic position for a human to be in, but many people find it strenuous to stay in a squat for an extended period of time. This is (most of the time) because people own chairs, don't spend any time in a squat anymore and have gradually lost the ranges of motion needed to access it.
This slow and simple class will lengthen the calves and hamstrings, open the hips and inner thighs, and create more range in the ankles, to eventually lead you into a sustained squat.