Grinding, an abrasive machining process, used to quickly remove material from a workpiece to reduce its size and/or to eliminate irregularities. Grinding process is done with the utilization of an abrasive tool called grinding wheel or plate, which rotates at speeds up to 1.000rpm and is commonly made of aluminium oxide, silicon carbide, diamond, among other materials
Lapping, also an abrasive machining process, but used to precisely remove material from a workpiece to produce surface flat, smooth and unpolished. Lapping process is done by rubbing the surface of the workpiece against another surface, the lapping wheel with an abrasive between them. Illustrative pics: