Femur and bearing
A hip resurfacing and total hip both involve relining the inside of the socket.
A resurfacing does not remove the entire head, but rather caps the head with a cemented metal piece. A total hip does replace the entire head, and the head is attached to a piece of metal that goes down inside the femur 5 - 6".
A critical difference is that a resurfacing requires a metal on-metal bearing (bad idea).