Drive belts operate using the force of friction to transfer power within the system. When a drive belt is installed, tension is applied. The tension then creates friction between the belt and the pulleys where it has been installed.
The crankshaft turns and transfers power to the camshaft, via a timing belt. This provides power to the drive belt via the camshaft, in turn, and causes the drive belt to move due to friction between it and the crank pulley. Lastly, friction between the belt and any accessory pulleys then causes them to rotate.
It should be noted that drive belts don’t last forever. Due to their composition, the rubber wears out through use and will typically degrade with time even if it has been reinforced using steel fibres. If a belt is worn, cracked, or otherwise damaged, it should be replaced as soon as possible to avoid downtime or damage to other components within the system.