what is this? and what does it do exactley?

 

i assume your talking about 2-step launch control? its like a secondary rev limiter that kicks in when your car is sitting still for launching in a drag race off the line. it allows you to have the gass to the floor (open throttle) and not have to focus on your rpm, but rather the tree. i use it and love it. youtube it and you will get the idea.