ABS is a commonly used thermoplastic polymer, comprised of acrylonitrile, butadiene, and styrene. (Hence ABS.) ABS has a higher mechanical resilience thanks to the butadiene rubber.
ABS will shrink as it cools after extrusion. When printing large parts, this shrinking will cause the printed parts to warp. Increasing the ambient temperature of the printer will reduce the shrinking effect.
When making mechanical parts, especially parts exposed to higher temperatures, ABS offers a great combination of heat resistance and strength compared to PLA.