What is a cam ON A CAR?

In a car, a cam (specifically, a camshaft) is a rotating component of the engine that controls the opening and closing of the valves. These valves control the intake of air and fuel into the cylinders and the exhaust of burnt gases. The camshaft's lobes push on the valve lifters (or rocker arms), which in turn open the valves at precisely timed intervals to ensure efficient combustion.