This is an origin that can be translated, scaled or rotated in Blenders Z-up coordinates.
This tool will hopefully give you a much better understanding of the coordinates in Blender. I think it is especially good for beginners or people comming for Y-up coordinates.
NOTE: There's an issue on Sketchfab. The Z dosn't look that awful in Blender. If it does, please let me know by mailing to hej[AT]vizy[DOT].dk