A machine is a tool containing one or more parts that uses energy to perform an intended action.  Machines are usually powered by mechanical, chemical, thermal, or electrical means, and are often motorized.  All of them are specifically designed to served human; reduces effort and saves time.  Historically, a power tool also required moving parts to classify as a machine.  However, the advent of electronics has led to the development of power tools without moving parts that are considered machines.