These are rapid back-and-forth shuttles with one step in between direction changes. Go two steps to the right, then two to the left.
This really focuses on lateral change of direction, and it's a great way to improve coordination and leg strength/power while building structural integrity in the lower body. Higher reps will scorch your quads and lungs.
With mechanical drop sets, instead of reducing the load, you switch to a new but similar exercise by changing the grip, angle, etc. The result is a whole lot of burning and a whole lot of growth.
So you spend maybe 5 or 6 hours a week in the gym. How much of that time is spent snapping towels or playing the soap dish game in the locker room? If you plan just a little and cut out the wasted time, you might actually build a decent physique.