This 2.5D work starts off as a 2D design in principle, but during the process of creating the tool path or cutting file you will typically assign a depth or multiple depths for the tool's motion to cut features like grooves or flat pockets. When the software generates the part file, the instructions will first move the CNC tool to the assigned cutting depth (in the Z axis), then move the cutter through the XY tool path at that depth, and then return to the starting height with a straight pull-up. Thus, when the file is finished, the cutting tool has moved in three dimensions (X, Y and Z), but all the X and Y axis motion is in a single plane and the X and Y axes stop when the Z axis plunges or pulls up. So, for the case of this example, the drawing and design process are fundamentally 2D. Standard cabinetmaking would be a good example of such a 2D or 2.5D project.
V-carving(2.5D) is a great way to add an impressive look to your lettering or sign work and decorative wood carvings. Importantly, because the layout process is still in 2D, it is relatively easy to create the designs, and from a production point of view v-carved letters can be cut fairly quickly.
If you are a professional signmaker or woodcarver, you are probably already aware of the importance of v-carving to your work.