The template is for drawing, well, regular polygons. I did my best effort in Blender to make all the polygon holes have the same side length, but I cannot ensure absolute perfection, only really really close to perfection. Any inaccuracies are caused by the 3D printing process, which is why the polygon holes may have rounded corners and the triangle may be too small, despite these imperfections not being in the 3D file.
If you want to, you can use a permanent marker to write numbers next to the holes indicating the amount of sides each polygon has. That is what I did in the photos.
For ideas on what to draw with this tool, check out this article on Wikipedia: https://en.wikipedia.org/wiki/Euclidean_tilings_by_convex_regular_polygons