CBMP. Just as an example. If you face a wall. Moving the shoulders as less as possible turn the feet down LOD. Place your RF and leg across the body. To sum up the leg moved and the shoulders didn't. This is esential on the second quick of a Feather Step prior to a Reverse Movement. Lady does the natural opposite.
If you understand the above, CBM is the shoulders ( side moves to the foot)as in the first step (slow) of the Feather. The first quick ( second step has neither of the above. There will be CBM on the first step of the Reverse Turn. I hope this hasn't confused the issue. It's reall simple to understand but to bring into action the use of the sides means the body must be, or become flexible.On top of this we need an understanding of Swing and Sway plus the music.Best of Luck.