A turret on a CNC (Computer Numerical Control) machine is a rotary tool-holder that is mounted on the spindle of the machine. It holds multiple cutting tools, and can rotate to bring a different tool into position for use. The turret allows for automatic tool changing during the machining process, which increases efficiency and reduces downtime. It is typically found on CNC lathes, but can also be found on some CNC milling machines.

CNC lathes have a turret that can hold multiple tools on it, and the tools are indexed, which means they rotate to bring the required tool into the cutting position. This tool changing process is done automatically by the CNC controller, which reduces the need for manual intervention and increases efficiency.

CNC mills on the other hand, normally have a spindle that can hold one tool at a time, but some milling machines have a rotating tool changer on the spindle, which is similar to the turret on a lathe.

Overall, the use of a turret on a CNC machine allows for faster and more efficient machining, by reducing the time required for manual tool changes and improving overall productivity.