Box and No Box

Will someone please define what a "Box" car is and what a "No Box" car is?

I assume they both have a transbrake but what makes one a Box and the other a No Box car? If the No Box supposedly does not have a delay box, how is that enforced???

Since I'm just an old-fashioned foot-brakin' 1/4 mile bracket racer, I see these other classes all the time but not quite sure exactly what they mean. Thx!!