Contouring milling is a machining process that involves the use of cutting tools to remove material from a workpiece in a series of successive passes. The process is used to create complex shapes and features on the surface of the workpiece, such as contours, pockets, and slots. Contouring milling is often used in the manufacturing of parts for the aerospace, automotive, and medical industries. The process requires high precision and accuracy, and is typically performed using a CNC machine.