Back when we crossed this country in covered wagons, the wagon brake had a mechanical linkage to a shoe, which pressed against the outside of the wagon wheel. Although wagons had no more than one brake for all four wheels, this braking method was effective for the weight and speed of the vehicle in question.
Drum brakes on different autos and trucks all work basically the same way. The differences are in the placement of springs, rods, and hydraulic cylinder. The springs pull the shoes inward, and rods keep the shoes in position, and provide a pivot point for the shoes to spread outward when activated. Both the springs and rods help stabilize the shoes so they put even pressure on the drum. No matter the configuration, they are all complicated enough to make you crazy, especially when trying to put all the pieces back together again.
Disk brakes have two brake pads positioned on either side of a metal disk. When braking, hydraulic pressure forces a cylinder to compress these two pads, gripping the disk, the friction slowing the wheel and the auto. Disk brakes work by a squeezing action.
Drum brakes have two padded shoes that face outward. When the driver applies pressure to the brake pedal, it sends hydraulic fluid through lines to the hydraulic cylinder between the two brake shoes. The cylinder's pen pushes outward, forcing the two shoes apart and against the inner lining of the brake drum.
Changing disk brakes is easy compared to drum brakes. Nonetheless, if you take your time and pay attention to what you are doing, you can change drum brakes without too much effort in a reasonable amount of time. Remember, replacement brake pads, disk or drum, could contain asbestos. Braking action produces ground material in the form of dust. Be careful not to breath in this dust. If you want, wear gloves and a surgical face mask.