Hi, Mr. Varbid,
I’ll explain with the simple example of pull-ups:
Suppose your routine is to do 10 pull-ups, rest, do 10 more pull-ups, rest, and do another 10 pull-ups. You are doing 10 pull-ups 3 times.
Or, you are doing 3 “sets” of 10 “reps” (repetitions). “Sets” refers to how many times you repeat the exercise. “Reps,” or repetitions, refers to how many times you repeat the given movement within the set.
Never perform less than 17 sets of any given exercise. Kidding.