Your timing belt, also known as the cambelt, allows the engine crankshaft to turn the camshaft that controls the opening and closing of the engine’s valves.
Cambelts are typically made from fibrous reinforced rubber and it is a common recommendation that they are replaced every 3 years or 60,000 miles to avoid the belt breaking and causing serious engine damage. You can check this in your vehicle handbook.
In some engines, the cambelt may also be used to drive other engine parts such as the water pump and oil pump.
A snapped cambelt normally results in cylinder head damage with repairs often costing hundreds of pounds.