Hopefully you didn't pay anything. It's pretty much what we call crossfit. A little high interval intensity training with bodyweight exercises.
The way it works is that it confines a lot of high intensity work into a small amount of space. The traditional way is to train at medium level for hours on end. HiiT however switches it up where you switch up the intensity levels between high and low. So in the end you expend the same amount of energy in a shorter amount of time. On top of that, because of the high intensity bringing your heart rate at peak levels, you'll have an after burn effect relevant to the time you spent at the higher heart rate.
