Torque-braking is when you put the automatic car in drive while holding the brake pedal while at the same time pressing the accelerator until the engine rpms max out, and then you let go of the brake pedal.
It is a stupid way to launch an automatic car faster, but it usually wear down the transmission. Many automatics will let you hold at 3500 rpms for good launch, but it overheats the transmission fluid.
Basically a poor man launch control.
However, even stock launch control systems put more strain on the transmission hence the warning about it use in the owner manuals.