Years ago it was called backspacing and it would be listed how much wheel was behind the hub mounting plate.
In today's jargon, it's offset ...
The offset of a wheel is the distance from the hub mounting surface to the center line of the wheel. The wheel offset is measured in millimeters and results in a positive, negative, or zero offset.
Positive offset (+25, +35, +40, etc.) is when the hub mounting surface is toward the face of the wheel. It is common to find a positive offset in newer and front wheel drive vehicles.
Negative offset is when the hub mounting surface is toward the back or brake side of the wheels centerline. A negative offset wheel usually has a "deep lip" or concave face.
Zero offset is when the hub mounting surface is even with the centerline of the wheel.
To accurately compare wheels you need to know the wheel width and offset.
Hope that helps & please feel free to correct any inaccuracies.
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