The scientific definition of a machine is any device that transmits or modifies energy. In common usage, the meaning is restricted to devices that perform or assist in performing useful work.

It normally requires some energy source ("input") and accomplishes some sort of work.

Machining is an occupation or hobby or a class of material-working processes that involves using a power-driven machine tool, such as a lathe, milling machine or drill, Machining Centre to shape metal.

Machining is a part of the manufacture of almost all metal products.

A milling machine is a machine tool used for the complex shaping of metal parts. Milling Machine Its basic form is that of a rotating cutter or endmill which rotates about the spindle axis, and a movable table to which the workpiece is affixed.

That is to say the cutting tool generally remains stationary while the workpiece moves to accomplish the cutting action.