Right, that explains everything.
Perhaps what I should have said is that it would take a lot to explain, more than I'm willing to devote in a forum like this, especially not knowing what level of technical competence the audience possesses.
I apologize, I thought everyone knew how normal printers work.
The printer receives the file from the computer. The file contains information stating were each pixel goes (x,y) and the printer puts that pixel there.
A 3D printer in the most simplest terms does the exact same thing with (x,y,z). I erroneously put y coordinate, it is a z.
A fine powdered layer of material (basically the paper) is laid down and a laser "prints" (turning the paper into the ink) the shape. What is printed hardens, the rest remains a powder.
A new layer is added on top (the z) and the process repeats itself.
I think the part can be made in either direction, it would be the same process.
I guess it is just
this, just with metal.