Note that the faces and vertices are all numbered from 1. I believe there are no gaps in the numbering for any of the meshes. The *_low.m meshes may have 3-7 sided faces in them. The *_hi.m faces should all be triangular. The vertices of the *_low.m meshes will almost always have valence 4.

The *_hi.m is made from the *_low.m mesh using the manifold process and is approximately what you would get from subdivision. The topology, however, is not subdivision topology. They'll still be fairly regular, though.