Clutch: Mechanical friction device that engages or disengages the engine from the transmission.
Read more
It is located between the engine and the gearbox. It is used to disengage the engine, which prevents the movement to be transmitted to the gearbox while the gear shifts are made. Roughly speaking, it is the piece that disengages the engine from the wheels when the driver presses on the clutch pedal.
My 2000 1500 Silverado started running when I was hauling something a few weeks ago and would cool down when I would turn it off. Then it started getting no matter what if I was hauling something or not so I changed the water pump, fan clutch, radiator, all new holes, new thermostat