The Big Question—What is 3D Printing? - 3D Printing: Build your Own 3D Printer and Print your own 3D Objects - page 18

Figure 1.11 A single layer of melted plastic in the shape of a square might use
one of these paths.
The thickness of the melted plastic is actually thinner than that of a pen (and its
ink), but you should get the idea. The hot-end acts like a pen, drawing a path on