I should add that I don’t know which type of lock it is, a deadbolt/springbolt/or nightlatch or what the difference is between those. The lock can be opened from the inside by pulling down on the handle. It locks when the door is shut. To unlock from outside you have to insert the key (tooth-side facing up) and then turn to the right about 20-45° the lock then pops open. It’s difficult to see in the picture but this is a Yale lock
