3D printing works in the same way a computer printer prints an ultra thin layer of ink on a page to form text. Except a 3D printer can print multiple layers of plastics and even metals to form three dimensional objects.
Generic mass produced objects may soon be a concept of the past.
One dad even printed a prosthetic arm for his son.
In the future, the 3D printer may very well be looked at as the first real replicator made famous from Star Trek.