Warm-ups can be split into two categories: General, getting warm and specific, which is warming up for the exact training movements.
Most intensive set with the heaviest load, most of the time performed with a primary exercise.
Back-off sets are additional sets of your primary muscle group or exercise for the day, but with lower intensity. Back-off sets focus on providing additional rep work on those same muscles groups without the intensity of your top set.
accessory work set
Accessory exercises incorporate one or more of the muscles used in the primary lift of the day.