sure this could have been answered on google,anyway when you lock your door normally and someone smashes the widow they can open the door from the inside. with deadlocks they cannot.
simple answer for ya
Ummm theyre just door locks but when they are locked and then dead locked on the central locking (on the stilo you have to press the button twice to hear it click) it just means the doors cant be opened inside or out or even if u pulled the lock thing up from the inside. So if someone were to break into your car they can't get the doors open.