Lock-offs are a 2BR comprised of a 1BR and a Studio with a connecting door. Some are used as a 1BR or a Studio and the connecting door is kept locked and others are used as a 2BR.
There are different configurations depending on the resort, but at most resorts dedicated 2BRs will have 2 Queen beds in the 2nd BR and will not have a balcony for that room. There are some different variations at BCV and BWV has no dedicated 2BR villas - all are lock-offs with one Queen bed and a sleep sofa in the 2nd BR. At OKW all studios have 2 Queen beds (no OKW studios have the sleep sofa).
Dedicated 2BR villas will no have a kitchenette in the 2nd BR and will also have only one exterior door for the unit. Lock-off 2BRs will have the kitchenette and the 2nd BR will have it's own entrance but all keys will open both doors.
At HH, the lock-offs are usually reserved only as Studios and 1BRs unless needed for a HCA unit (there are only a couple of those at the resort).
Some prefer the dedicated 2BR when they have small children in the room (due to the lack of the exterior door in the 2nd BR). Others prefer the lock-off when they have 2 couples staying in the room so each will have a private entrance.
Enjoy!