A workpiece is a piece, often made of a single material, that is being processed into another desired shape (such as building blocks).
The workpiece is usually a piece of relatively rigid material such as wood, metal, plastic, or stone. After a processing step, the workpiece may be moved on to further steps of processing. For example, a part can made out of bar stock and later become part of a semi-finished product.
The workpiece is often attached to the tool being used via a jig or fixture, like for example to a milling machine via an angle plate, or to a lathe via a lathe faceplate. A vise is another example of a simple type of fixture used to fix workpieces.
A workbench is often used to hold a workpiece steady during work on it.