This document provides an overview of hydraulic brake systems. It describes how hydraulic brake systems use brake fluid under pressure to activate brakes and create friction to stop a vehicle. It outlines the basic components and operation of hydraulic brake systems, including the master cylinder, combination valve, brake lines, wheel/slave cylinders, wheel calipers, brake pads/shoes, and brake drums/rotors. Routine maintenance of hydraulic brake systems involves periodic cleaning, inspection, and adjustment of brake pads/shoes, as well as fluid changes when discolored or containing high moisture. Safety precautions are required any time working on or around brake systems.