This set of buttons controls the heat settings for the timed dryer cycles.
If you press any of the top four buttons, they stay depressed. If you then press a different button, the first one pops up, and the new button stays pressed in. A really neat set of plates that work like the tumblers in a lock make this feature possible, and also control which heating elements are engaged.
Inside the switch are a set of four contacts. Depending on which button is pressed in, the plates open or close various combinations of the contacts. The following set of pictures illustrates how pressing the buttons causes the plates to line up in different ways, raising or lowering the bars that make the contacts.