The major difference is that grinding involves the removal of a significant amount of material from the surface. Grinding is necessary for removing saw marks and any other tangible defects on the surface. Grinding does not give you the final finish that you want on a surface. Even though it can remove rough edges, it will still leave the surface looking dull. Polishing, on the other hand, is a much finer type of grinding. The abrasives for polishing are microscopic particles. Also, it will only remove a tiny bit of material from the surface.