3D printing is an abbreviation for three-dimensional printing.
3D printing (or additive manufacturing) is a process of making three dimensional solid objects from a digital file.
The creation of a 3D printed object is achieved using additive processes. In an additive process an object is created by laying down successive layers of material until the object is completed.
3D printing is the opposite of subtractive manufacturing, which is cutting out / hollowing out a piece of metal or plastic with - for instance - a milling machine.
3D printing enables the production of complex shapes using less material than traditional manufacturing methods.
It also enables faster delivery of physical objects, by transmitting an electronic CAD file containing the design to a local printing machine, shortening the distance that the physical object is transported.