Anti-Squat is best described as Caster for the rear wheels…it changes the relation of the hinge pins parallel to the ground.
Adding Anti-Squat will make the car Squat less during acceleration. This will cause your car track straight on the straights. It will also make your car push coming out of corners, but loose entering corners.
Less Anti-Squat will result in the opposite: a little less forward traction, more stable entering corners, and will track through bumpy sections much better.
Anti-Squat is most effective from a standstill.
To change the Anti-Squat on the RC18-Series vehicles, simply remove the rear arm mount, flip over and re-install.