What's the difference between a Deadbolt and a Deadlatch
A deadlatch refers to a self latching bolt which usually has a 45 degree angle on one side, and can close or lock when the door is pushed closed. It has an extra little trigger that when depressed locks out the larger angled latch making it deadlocking.
A Deadbolt is a bolt which must be thrown by turnsnib or key, and will not automatically become active. The bolt is usually square from from a side profile. Other types of deadbolts are the Lockwood 355 which has solid pins that must be activated.
Here are 2 examples of each type below.