This section of the car is used to generate and transmit the power that turns the wheels and allows the car to move. It also controls how fast the wheels rotate, and how much force they turn with.
In the engine, the valves control the flow of fuel and air. This in turn controls the explosions which move the pistons up and down. The up-and-down movement will in turn rotate the crankshaft, and it is this rotation that is transmitted through the clutch to the gearbox.
The movement of the valves is controlled by the camshaft, a series of rotating plates that force the valves to move up and down. At the end of the camshaft is a cog that attaches to the timing belt. The timing belt, powered by the movement of a similar cog at the end of the crankshaft, ensures all these parts move in sync.
In the gearbox, gears are selected by moving the pivoted gear stick to different positions, which slides series of cogs within the gearbox back and forth. Different arrangements of cogs determine how many times the clutch shaft (the shaft from the engine) needs to turn to rotate the transmission shaft (which powers the wheels). This controls both the speed and force of rotation.
In a front-wheel-drive car (as pictured here), the differential sits next to or behind the gearbox, and the drive shafts which power the front two wheels feed directly into this, at right angles to the transmission shaft. The arrangement is different for a rear- or 4-wheel drive car.