A master cylinder is a crucial component in a vehicle's hydraulic braking system. It converts the force applied to the brake pedal into hydraulic pressure, which then activates the brake calipers or wheel cylinders. This process allows the vehicle to slow down or stop effectively. Typically made of metal or plastic, the master cylinder contains a reservoir for brake fluid. When the brake pedal is pressed, a piston inside the master cylinder moves, pushing the brake fluid through the system. This action ensures that the brakes respond quickly and efficiently, enhancing overall vehicle safety.