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

The crankshaft converts the reciprocating motion of the piston into the rotational motion that's used to power the vehicle and its components.

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.

Spark plugs receive current from the distributor and use it to spark combustion in the combustion chamber of a cylinder.