The absolute maximum is sometimes also called the global maximum. As low as it can get. Drop the negative sign if there is one. Otherwise, just leave the number alone.
Acceleration is the rate of change of the velocity.
It causes that funny feeling in the pit of your stomach as you are mushed backward into the seat when somebody really puts the pedal to the metal. Since the rate of change of a function is its derivative, the acceleration is the derivative of the velocity function.