What is the role of brake drum in automobile braking?

Someone may ask what is a brake drum? What is the role of the car brake? Now let me give you a brief introduction.

The brake drum is only used for low-end cars or trucks, and buses. It is a part of the drum brake system. When braking, the piston exerts pressure on two pairs of half moon brake shoes to make them cling to the wall of the drum chamber, thus producing friction to stop the rotation of the wheel,

To put it simply, it is used to wear the brake pads. It brakes by friction with the brake pads - stop/reduce speed. The clearance of the brake drum should be adjusted regularly, and the two sides should be the same, otherwise the brake will deviate (very dangerous)

The advantage of this brake drum is that it has good effect and low price, but the heat dissipation is not very good, especially in long downhill. So the big trucks have water spray on the wheels.