What is a 3D Printer (FDM)?
Basically, a 3D printer pours melted plastic out in lines that stack on top of each other, to form a desired shape.
A spool of plastic material called filament is pushed through a tube then heated and pushed out in very thin lines:
While pushing plastic out, the printer can move in three directions:
This combination of movement and plastic extrusion allows a 3D printer to create all sorts of objects: