How do air brakes on semi's work?

This is going to be long but, heres how it goes. The air governor controls the air compressor to pull in the air from outside, the air compressor than compresses it into very small amounts, the air than goes though the air lines to the air dryer. Here it is basically cleaned of any moisture and debri, after that it continues to the air tank where it is stored for use. When you push on the treadle valve or foot valve, or in normal terms the brake pedal a valve is opened in the air tank which allows the air to escape though the air lines, when it gets to the brake mechanism the force of the air actually pushes against a slack adjuster which in turn, turns an S-Cam which pushes the brake shoes against the brake brum, which in turn creates friction and brings your commercial motor vehicle to a stop.

SIMPLE AS THAT