What a clutch is and does

There are a number of mechanisms involved in converting the turning motion produced by a car's engine to the turning motion of the wheels. These are the clutch, gearbox, propeller shaft and final drive.

These 4 items together are called the "transmission". Whenever the engine is running the crankshaft is turning . The clutch is the connection between the rotating crankshaft and the gearbox.

When the clutch pedal is in the normal "up" position (engaged) the plates in the clutch press together and transfer the turning motion to the gearbox. In "neutral" no gear is selected so this motion is not passed on to the road wheels and the car stays still. When a gear is selected the gear wheels engage and the motion is passed on to the wheels.

When the clutch pedal is pushed "down" (disengaged), the plates in the clutch are pulled apart a little and the turning motion is not passed on to the gearbox.