These are Pathfinder rules used for their reduced rolling, melee options now more comprehensive and useful, and to reduce the gap between high level monsters and adventurers. This also allows for more varied builds. Want to be a tripper? Don’t have to be a STR build anymore. Allows Jackie Chan some fun.
During combat, you can attempt to perform a number of maneuvers that can hinder or even cripple your foe, including; bull rush, disarm, grapple, overrun, sunder, and trip.
Although these maneuvers have vastly different results, they all use a similar mechanic to determine success.