I'll take a shot...it's really pretty simple, the term "box" is referring to the delay box (basically a timer) built by numerous manufactures that allows you through practice and learning your body's reaction time combined with your cars reaction time to release the transbrake button on the top bulb instead of footbraking off of the bottom bulb. The advantage is that it allows you to train yourself to leave off of the first flash of yellow on the top bulb rather that "guessing" when yellows go off or come on based on your and your cars reaction to the bottom bulbs, lots of guys are really good footbrake racers but to me it's much easier to train your eyes and body to leave off of the first flash of yellow at the top of the tree. There are now crossover delay boxes that will do the math for you based on you and your opponents et, back when I started using delay boxes we had to carry a calculator to work the difference so I could leave off of the opponents top yellow...hence being able to leave on the first flash of yellow, since most trees are shielded nowadays it doesn't matter, you just leave off your side of the tree and the delay box does the math...NORMALLY...a box racer has a sizeable advantage over a footbrake racer (due to more consistent and better lights) which is why at most tracks they separate the classes. I hope this helps maybe others will chime in...I have grossly oversimplified the process but maybe it helps a little.