3D Printing

3D printing or additive manufacturing is a process of making three dimensional solid objects from a digital file. It is additive because it is created by adding successive layers of materials until the whole object is created.
Firstly, a virtual design of the object you want to create. This virtual design is made in a CAD (Computer Aided Design) file using a 3D moelling program (for the creation of a totally new object) or with the use of a 3D scanner (to copy an existing object). A 3D scanner makes a 3D digital copy of an object.

Processes and mechanisms 

All 3D printers don't use the same technology. There are several ways to print and all those available are additive, differing mainly in the way layers are build to create the final object.
Some methods use melting or softening material to produce the layers. The most common technologies using this method for printing are the Selective laser sintering (SLS) and fused deposition modeling (FDM). Another method of printing is when we talk about curing a photo-reactive resin with a UV laser or another similar power source one layer at a time, stereolithography (SLA) is the most common printer using this technology.

Examples & applications of 3D printing

Applications include rapid prototyping, architectural scale models & maquettes, healthcare (3d printed prosthetics and printing with human tissue) and entertainment (e.g. film props).
Other examples of 3D printing would include reconstructing fossils in paleontology, replicating ancient artifacts in archaeology, reconstructing bones and body parts in forensic pathology and reconstructing heavily damaged evidence acquired from crime scene investigations.