Dumb question:
 

Alright i'm sure this is dumb but i'll ask regardess.Can anyone please explain to me what "Brake boosting" is?

"The race: 3rd gear punch, i brake boosted..." <---Example

So that's what is meant??

If not the how stuff works explanation its probably a way of saying he left foot braked while holding the gas pedal down. You can do this in a turn to spool a turbo up without speeding up but I don't know why you would want to do it in a straight line racing.