XY Scale

This is a simple test to check if your printer actually prints "at scale". Once printed and measured, you can either change the settings in your printer's firmware (steps per mm on the X and Y axis), or just learn what scaling you need to apply in your slicer.
This is important for parts that have holes in them, and also to have consistent dimensions in multiple parts prints, when you might not be able to have all parts printed in the same orientation.