This is one of those parts that helps with 3D printer calibration.

The first version ("Overhang Angles") has 5 walls that are 15, 30, 45, 60, and 75 degrees from the build plate, which are labeled on the top. Those help fine-tune support, wall/shell, and resolution settings, along with several vertical walls for comparison.

The second version ("Material Test 2") has vertical posts on top to help calibrate retraction and travel settings, along with 30 and 60 degree overhangs on the sides, and a hole in the bottom to test "bridging" and flat supports.