The Big Question—What is 3D Printing? - 3D Printing: Build your Own 3D Printer and Print your own 3D Objects - page 16

Figure 1.10 Top view of a 3D printer lets you see the X and Y axes.
Looking at a 3D printer from above, you can now see that when the hot-end moves
left or right (when viewed from the front of the 3D printer), it's actually moving