Sets in gym refer to a group of repetitions of an exercise performed sequentially. For example, if you perform eight repetitions of bench presses, that would be one set. Repetitions, or "reps" for short, refer to the action of one complete strength training exercise, such as one bicep curl. The number of sets and reps you do will depend on your experience level with resistance training and your fitness goals. A workout plan may include instructions to do a certain number of sets and reps for each exercise, with time built in for a short rest between sets. Using sets and reps to organize your workouts can help gauge your baseline strength, measure progress, and reduce the chances of accidentally overdoing it and injuring yourself.