Chemical Mechanical Polishing (CMP) is a process used to planarize and smooth surfaces of semiconductor wafers and other substrates. It is a combination of chemical etching and mechanical polishing that uses a slurry containing abrasive particles to remove material from the surface of the substrate. The slurry is applied to the substrate and a polishing pad is used to apply pressure and friction to the surface. The combination of chemical and mechanical action removes material from the surface and creates a smooth, planar surface.