THERE ARE MANY TYPES OF LOCK FUNCTIONS.
You probably have never realized that locks can do so many things. It doesn’t’ have to be a fancy lock, just a plain lock with a function you may have never thought of.
Locks have been used for centuries and have been developed to do many things. Just think about it a moment.
The difference of the closet hallway door knob when compared to the front door knob.
A passage lock function is closet door knob, It isn’t meant to restrict entrance so it doesn’t have a built in cylinder for a key to go into.
A privacy lock function is a Bathroom door knob, you can lock it from the inside but with a little tool anyone can open it from the outside. It isn’t meant for security, just privacy
An entrance lock function, for security, key required to unlock from outside, when locked, unlock/lock from the inside. Some of these can only be locked from the inside.
A storeroom closet function, always locks when you close the door, always unlocked from the inside
A Classroom function key locks or unlock outer knob or lever, inside always unlocked (no way to lock without a key)
A single sided dead bolt. Key required to lock or unlock on the outside, inside open with a thumb turn
A double sided dead bolt key required on both sides to lock or unlock. Used for a front door next to a window, so entry can’t be made by breaking the window and turning the knob.
I almost forgot one of my favorites.
A latch bolt Locks when you close it from the outside and a thumbturn from the inside
This is also made as a double sided latchbolt with keys need on both sides. You see this a lot at clubhouse pools.