What's the difference between a timing belt and a timing chain?

Both a timing belt and a timing chain do the same job: keeping the engine's crankshaft and camshaft turning in sync, so the valves open and close at exactly the right moment relative to the pistons. The difference is what they're made of, and what that means for maintenance.

A timing belt is a reinforced rubber belt, and it has a manufacturer-specified replacement interval, commonly somewhere between 60,000 and 100,000 miles depending on the car, regardless of whether it looks worn. It needs to be replaced on schedule because it can fail without much warning.

A timing chain is metal, and generally isn't on a fixed replacement schedule - it's designed to last the life of the engine, though it can still stretch or wear over a very high mileage and need attention eventually.

For a buyer, this matters a lot on a belt-driven engine: on most modern engines, if the belt fails, moving parts inside the engine can collide with each other, causing serious, expensive damage. It's worth knowing whether a car you're looking at has a belt or a chain, and if it's a belt, when it was last replaced and when it's next due.