[metallion]

Oddly enough this simple concept can be a bit hard to describe in text, but here's an effort. Just keep asking. I did and I will.

The is ball laying on a Straight Plane Line.

There is an infinite plane cutting through that Straight Plane Line.

Any time the clubshaft does not lay on the plane is is off plane.

The angle between the plane and the ground may vary during the swing, but the plane will always cut through the same Straight Plane Line.

At Impact Fix the angle between the plane and the ground is determined by the lie of the clubhead and the forward lean of the shaft. So basically the angle varies between clubs with different lies.