Timing belt (camshaft)
In a piston engine, a timing belt (also called a cambelt) is a toothed belt that drives the camshaft and synchronizes its rotation with the crankshaft propelling it. This synchronisation ensures that the engine's valves open and close at the correct times in relation to the position of the pistons. A timing belt is a semidurable component: in many cases it lasts for the service life of the engine, and in other cases it must be replaced during the engine's service life, anywhere from once to several times, depending on how the vehicle is used and how long the vehicle is in service.
Many modern engines have timing belts; others instead have either a timing chain (which is a roller chain with the same purpose) or a set of timing gears that mesh with one another.