The catalytic converter converts pollutants in exhaust gas into less pollutant substances like carbon dioxide and water.

The engine (or cylinder) block is the large casing that contains the cylinders and many of the internal components of the engine.

Combustion is the burning of an air-fuel mixture to provide energy. It requires the presence of air, fuel, and a heat source to ignite the air-fuel mixture. In the internal combustion engine that powers automobiles and trucks the combustion happens inside the engine utilzing a fuel like gasoline, diesel fuel, or natural gas.

The master (brake) cylinder converts pressure on the brake pedal to hydraulic pressure in the brake lines.

The transmission provides the appropriate power to vehicle wheels to maintain a given speed. The engine and the transmission have to be disconnected to shift gears and a manual transmission requires the driver to manually manage this disconnection (using a clutch) and to manually shift gears. An automatic transmission is essentially an automatic gear shifter and handles this process without driver input.