"locked diff" = no differential (welded gears, or spool replaces the differential)

Limited slip is what you want for the street if you are having a traction problem

The "ratchet locker" your Surf has might be a sort of hybrid, like the famous ""Detroit Locker". What's a Surf anyways?

Some offroad vehicles have an off/on locker, like the famous ARB air locker. It is manually locked and unlocked using a switch in the passenger compartment.