maybe this will explain it better:
http://www.1010tires.com/wheeloffsetcalculator.asp
the reason we care about offset is to get the wheel to fit without sticking out past the fender (outer edge of wheel) or rubbing the suspension (inner edge of wheel)
offset is not used to change the look of the wheel itself, that is manufacterer's job. if you dont like the look of the lip on the wheel, get a different wheel