ABS (Anti-lock Braking Systems) was originally developed for aircraft applications.  ABS allows the driver to maintain directional stability and control with their steering, while preventing the wheels from locking up (ceasing rotation) and avoiding uncontrolled skidding.  ABS was designed to work to reduce stopping distances during an emergency braking situation.  ABS typically engages on wet or other slippery surfaces (such as snow, dirt, or gravel).