The third and final fundamental that I would like to define for you is called The Swing Plane. The swing plane is a hot topic amongst teaching pros. Everyone seems to have an opinion, but indeed perhaps a disagreement.
Key Elements of the Swing Plane
Let's look at what's truly important in the swing plane looking down the target line. How you use the shaft? How you use your arms? And how you use the shoulders? Will all have an effect on what happens in the backswing plane, the downswing plane, and the plane into the finish.
The importance of this plane discussion cannot be over estimated because if you have your club swinging on too shallow, too flat of plane, you will need to manipulate the face through impact and that will cause inconsistency.
If you have the club coming too much in front of you, too vertical or steep plane, you'll swing across the line of play and indeed again have to manipulate the club to get good consistent impact. Plane itself is a combination of what's happening with the levers and what's happening with the balance, it brings together those first two fundamentals to produce very efficient, trajectory correct golf shots.