A machine tool is any machine used in the manufacturing process and includes mills---both CNC and manual---and lathes of both varieties. The CNC machine tool has revolutionized the manufacturing industry by bringing speed and accuracy to the task of making parts. Mills CNC mills were invented in the 1940s and can perform complicated cutting, boring and drilling operations on thousands of parts with speed and accuracy. These machines come in many sizes, from small footprint versions to very large models capable of cutting material over 6 feet in size. Lathes CNC lathes are perfectly suited for simple, short production runs and are capable of performing more complicated cutting. They use a computer program to make very labor-intensive parts that require multiple types of cutting operations. Benefits The benefits of a machine tool over manually manufacturing parts is the accuracy that the machine tool can provide. In the case of CNC machine tools, speed is also a major factor in its supremacy over hand-working metals and other materials. Source: ehow.com