offset and backspace...

i have yet to grasp these concepts. when someone on here talks about wheel sizes and mentions backspacing and offset i'm clueless. someone fill me in please!

Backspacing is how far away the wheel mounting surface is from the rear lip of the wheel.  Backspacing is usually measured in inches. Offset is how far away the wheel mounting surface is away from the centerline of the wheel.  Offset is usually measured in millimeters.  Positive being more towards the front of the wheel than the centerline, and negative being more towards the back than the centerline.

Check out this link it will help you understand it. http://www.wheelspecialists.com/wheel-specs  

ok noooooow i get it. thanks guys.