[truckster]

A locker of any type uses mechanical gears to lock the differential under unequal loads, as opposed to a limited-slip (Positraction) that uses clutches to lock the differential. There are different types of lockers, and several manufacturers, but that's the basic difference. Some users don't like the chatter or noise they get with lockers on the street, but others don't seem to even notice. There are a number of threads on the board discussing the merits of different manufacturers' lockers.