Let's say you want to print a 10mm diameter tube with a 5mm diameter hole with its center at 0, 0, 0 XYZ position.
If you adjust the
Global offset Z-axis by 10 mm, it would now print the object center at 0, 0, 10 XYZ position. This is most often useful if you find your printer nozzle is some distance too far / too near to the bed, while most printers nowadays allow you to adjust the z-offset, it's not always the case / it might not be working correctly.
Size compensation is usually important for tuning for dimensional accuracy, you can read more here:
https://www.simplify3d.com/resources/pr ... -accuracy/
But here are the basics:
If you adjust the
Outer Size Compensation by 1 mm, it would result in printing a 11mm diameter tube with the same 5mm hole.
If you adjust the
Inner Size Compensation by 1 mm, it would result in printing a 10mm diameter tube with a 4mm hole.