Okay kiddo, imagine you are riding your bicycle and you want to slow down or stop. You might start by squeezing the brakes with your hands. Well, in a car or other vehicle with a manual transmission, there is something similar called a clutch. When you want to change gears or slow down, you use the clutch instead of the brakes!
Now, let's pretend that you have a bike with gears like a grown-up bike. When you want to shift gears on your bike, you have to use your hands to move the shifter to the correct position. In a car, the clutch helps you move the gears. When the clutch is pressed down with your foot, it disconnects the engine from the wheels, so you can easily change gears. When you let off the clutch slowly, it re-connects the engine to the wheels so that the car can move.
Here's the trick - the clutch is actually made up of two disks (sort of like bicycle brake pads) that are squeezed together to connect the engine to the wheels. When you press the clutch pedal, the two disks are pushed apart which disconnects the engine from the wheels. When you release the clutch pedal, the two disks come back together to connect the engine to the wheels again.
So, in short, the clutch is a pedal in a car that helps change gears by connecting or disconnecting the engine and the wheels using two disks squeezing together or apart.