[70ss396camaro]

I searched this forum but couldnt find info.Last weekend I was in Las Vegas at the big-o nationals.I came up from the concessions and some dragsters were running .It was loud and I couldnt hear what class they were.They were launching hard and then coasting to about the 330' mark and stomping on it again.I was in another area of this website yesterday and was told this is Super Comp and they are using throttle stops.They directed me to this forum area.I am not new to racing.I have watched drag racing for 30 yrs,have a 70 camaro I race in the 8th,bracket racing for the last 5 years,etc.I have heard of throttle stops,but didnt know what they were for,and didnt think they applied to me, so never asked.
So my questions;What is the game? if it is not normal dial in,heads up etc?
Is it just dragsters?What is the purpose of the throttle stop?Any info or a explanation would be greatly appreciated.................Thanks