CNC machining, or computer numerical control, is the automation of tools by computers running programmed sequences of commands to bring out a finished product. They can be set to provide a wide range of services and put together many functions to either add on to a product, or finalize it.
In modern times, CNC systems are a major part of manufacturing. A large portion is automated and set to a specific design that you choose. These machines combine all the tools you need for a product into a convenient cell to house them all and bring them out when necessary to use.