An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the work piece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflective surface, the process can also involve roughening as in satin, matte or beaded finishes. In short, the ceramics which are used to cut, grind and polish other softer materials are known as abrasives.
Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool.
A wide variety of machines are used for grinding: Hand-cranked knife-sharpening stones (grindstones), Handheld power tools such as angle grinders and die grinders, Various kinds of expensive industrial machine tools called grinding machines, Bench grinders.