Brakes are devices that inhibit motion and oppose relative movement. There are several types of brakes including air brakes, vacuum brakes, and hydraulic brakes. Drum brakes cause friction by pressing brake pads or shoes against a rotating drum. The main parts of a brake system include the master cylinder, connecting lines, brake pedal, disc brake arrangement, and brake pads or shoes. Brake fluid is used to transfer pressure from the master cylinder through the connecting lines to the brake mechanisms. Brake pads are plates with friction material bound to the surface that faces the rotating brake disc or rotor.