A clutch connects and disconnects a vehicle's engine from its transmission. It allows the driver to smoothly start from a stop, change gears, and stop the vehicle while in gear. A clutch operates using friction between two surfaces - the clutch disc and pressure plate. When engaged, spring pressure holds the surfaces together to transmit torque. When disengaged by pressing the clutch pedal, the pressure is released and power is cut off. Common types are single and multi-plate clutches, with multi-plate versions able to transmit more torque due to multiple friction surfaces.