The way your body grows/progresses is through something called Progressive Overload. Basically, you introduce a stress (ie Training). Your body will respond to the stress appropriately to make sure that you can do it again in the future. It will heal any 'damage' to muscle, nerve, tendon and organ cells. If the stress is sufficiently high, it will make the cells stronger (better able to adapt to future stress). That may mean bigger muscles, faster nerve impulses/communication, less fat. The key is to constantly improve/increase the stress within your body's capacity to adapt. If it is an outrageous demand, the body will not waste the resources on growth/progression. If it is too low demand, the body will not need to. There is a sweet spot. You will know where it is. What is important about this program is that the workouts are targeted to achieve this adaptation in as fast and efficient a manner as possible. That's why the workouts are shorter. If you do your sets well, with full attention, your body will respond. Less is more.

Now for some primers on workout terminology. If you know this stuff, just bear with me.

A rep is an individual movement of a given exercise within a set, ie how many pushups you do.

A set is a group of consecutive repetitions ie 1 set of 12 repetition (1x12).

Specifically, you need to know what a working set and a warm up set is.

A Warm up set will not be written down. It is a less formal set, that is there to ease your way up to your maximum capacity. If a wolf started chasing you, you would sprint, jump or punch at maximum capacity. But there are no wolves at your gym. Except for you. So we need to 'ramp' our bodies up to potential. The more intense the set (more weight) the bigger the ramp must be. So if you are squatting 300lb x 5 reps, you will need to do a few warms up first. It might look like this: 1 set of 5 reps at 135lbs, 1 set of 3 at 225lbs, 1 set of 1 rep at 275lbs. Then you move to your Working set of 300lbs for 5.

A Working set is a set at your maximum capacity. It is a serious set. You are not holding back. These are the sets that will be highlighted and recorded in the program. These are the sets you will record for your own purposes and make sure you beat the next week. If the plan for the day says Inc Bench Press (1-3) (3-5), then you will do a few warm up sets before your two working sets (the first one will be 1-3 reps and the second will be 3-5).

Dont worry, its really simple.