The difference is actually the focus of the software. Cad focuses on the design, hence computer aided design, and preferably uses nurbs. "Modeling" software focuses on the model; the poly count, triangulation, normals, typically uses poly meshes, etc. If you go to any of the cad software sites, the description will say cad software. The other software says modeling/animation/rendering. I'm just confused on how one industry is calling it differently than other 3d software industries and even the software devs themselves.