Hello,
I found this on wikipedia:
" The mouse acceleration, in the majority of mouse software, refers to the setting allowing the user to modify the cursor acceleration: the change in speed of the cursor over time while the mouse movement is constant.
For simple software, when the mouse starts to move, the software will count the number of "counts" received from the mouse and will move the cursor across the screen by that number of pixels (or multiplied by a rate factor, typically less than 1). The cursor will move slowly on the screen, having a good precision. When the movement of the mouse passes the value set for "threshold", the software will start to move the cursor more quickly, with a greater rate factor. Usually, the user can set the value of the second rate factor by changing the "acceleration" setting."
The full post can be found [http://en.wikipedia.org/wiki/Mouse_(computing)#Mouse_speed|here].
Hope this helps :)