The document discusses hydraulic braking systems, which use pressurized brake fluid to transmit force from the brake pedal through the master cylinder to the brake calipers or wheel cylinders. Hydraulic braking systems can be operated by vacuum, hydro or motor assistance and use either disc or drum brakes. The master cylinder contains pistons that provide a reservoir for brake fluid and transmit pressure equally to all wheels through the hydraulic circuit. Brake fluid must have properties like not thickening with heat, high boiling point, compatibility with brake components, and lubricating and non-evaporating qualities.