Can someone go into detail on what the difference is between backspacing and offset?

Thanks for the help

 

Offset refers to the measurement taken from the center of the wheel to the mounting surface on the hub. Backspacing is simply the measurement from the mounting surface of the wheel to the hub to the rear edge of the wheel. For instance, an 8 inch wide wheel that has the mounting surface to the hub in the center of the wheel would have 0 offset and 4 inches of backspacing. Most wheel companies refer to backspacing now, as it is much easier to measure and visualize. Here's a pic that shows how to measure backspacing. This wheel has 4 1/2 inches of backspacing.