Additive manufacturing uses data Computer-Aided-Design (CAD) software or 3D object scanners to direct hardware to deposit material, layer upon layer, in precise geometric shapes. As its name implies, additive manufacturing adds material to create an object. By contrast, when you create an object by traditional means, it is often necessary to remove material through milling, machining, carving, shaping or other means.
Although the terms "3D printing" and "rapid prototyping" are casually used to discuss additive manufacturing, each process is actually a subset of additive manufacturing.
This quite impressive “performance record” of Additive Manufacturing (AM) is one of the reasons why this technology is supposed to experience steep growth in the future.