The brake shoe carries the brake lining, which is riveted or glued to the shoe. When the brake is applied, the shoe moves and presses the lining against the inside of the drum. The friction between lining and drum provides the braking effort. Energy is dissipated as heat.
Modern cars have disc brakes all round, or discs at the front and drums at the rear. An advantage of discs is that they can dissipate heat more quickly than drums so there is less risk of overheating.
The reason for retaining drums at the rear is that a drum is more effective than a disc as a parking brake.
Brake linings are composed of a relatively soft but tough and heat-resistant material with a high coefficient of dynamic friction (and ideally an identical coefficient of static friction) typically mounted to a solid metal backing using high-temperature adhesives or rivets. The complete assembly (including lining and backing) is then often called a brake pad or brake shoe. The dynamic friction coefficient "µ" for most standard brake pads is usually in the range of 0.35 to 0.42. This means that a force of 1000 Newtons on the pad will give a resulting brake force close to 400 Newtons. There are some racing pads that have a very high µ of 0.55 to 0.62 with excellent high-temperature behaviour. These pads have high iron content and will usually outperform any other pad used with iron discs. Unfortunately nothing comes for free, and these high µ pads wear fast and also wear down the discs at a rather fast rate. However they are a very cost effective alternative to more exotic/expensive materials.