A CNC mill is primarily used for machining parts directly from CAD models, offering precision and the ability to produce identical parts with minimal user intervention. It provides significant flexibility, allowing users to create complex shapes easily. Users can also convert hand drawings or existing parts into CAD designs for machining. The discussion touches on the potential for CNC mills to create various items, including engine blocks and canisters. Overall, CNC milling is a versatile tool in manufacturing and design.