The main difference between a latch and a deadbolt is the mechanism utilized for locking. A latch uses a spring in the locking mechanism – it has a bolt, but you can see the bolt and where it locks into the strike plate (which is on the door, rather than inside of it). Deadbolts, on the other hand, are thicker and use heavier types of metal. They go inside of the door frame and hold the entire door secure with its mechanism. Deadbolts use turn knobs, keys, or automated motors in order to lock into place (but never, ever spring mechanisms).