...what would be the difference between the target and the plane line? Would they not be along the the same line?
The Impact Plane Line is in front of you and down on the ground. You swing the Club Down and Out toward that Plane Line and through it toward the Low Point Plane Line.
The Target, on the other hand, is well to your left...way out there...somewhere. Steering the Club on a Line to that distant Target is completely different than swinging Down and Outtoward the Plane Line down and in front of you.