Reps is short-hand for "repetitions" so it is how many times you repeat the same exercise in a set. number of sets in turn is how many time you repeat the whole "set" So like the example mentioned in the other ans, to do 5 sets of 20 reps for push-ups mean u will be doing 5x20=100 pushups.
The liver makes sure that blood glucose levels remain steady. But when blood glucose levels fall, the pancreas secretes glucagon. Therefore the answer to your question in the pancreas.
