An N-body test finds possibly colliding pairs of objects, A hierarchical oriented bounding box test finds possibly colliding pairs of triangles, and An exact test determines whether or not a pair of triangles actually overlaps.
The N-body routine uses coherence between successive time steps of a simulation to perform well in animations and moving simulations. The hierarchical Oriented Bounding Boxes (OBBs) and exact collision routines are taken from RAPID, a component of V-Collide which is also available as a stand-alone package.