If it is set to 1, it is on yes. If you want it off, have it = 0.
Mouse acceleration is a tool used to make casual mouse use easier. Without it, physical mouse movement to on-screen movement is 1:1. With it on, as you move the mouse farther and farther across the screen in one motion it will speed up your mouse by skipping pixels to help you get to the other side of the screen faster. This is detrimental to games because it means that there are "dead zones" where you CAN'T aim in one motion because of the acceleration.