A butt hinge joins a door and a jamb in the surfaces which abut. The plates of a butt hinge hook to the wood with screws and take the weight of the swinging door by pivoting on a pin.
Adding the doorway to the jamb so it may fold a butt hinge has to be quite powerful to carry the weight.
This is the trap that the butt hinge pivots on.
Doors typically use a few sets of hinges based on the height and weight of your door.
Don Duffy Architecture
Most hinges are recessed into the wood. Hanging doors correctly is a craft in itself.