No, this is not a bra commercial. We are talking about Smooth Dancing. When you first start learning Smooth Dancing, you basically treat your body as one piece from the hip sockets to the top of your head. As you progress to more advanced dancing, you need to start moving your body as separate parts. This separate movement allows you to create different shapes. Different shapes allow you to do things like "outside partner", "lock steps", "promenade" and etc.
Let's look at Quickstep. The difference between "closed dance position" (with left side lead) "outside partner" and "lock steps" is the amount of shape. The separation is between the bottom of the rib cage and the top of the hips (the soft area in between.). That soft area allows the separation of movement between the shoulder section and the hip section. The amount of hip movement enables you to have a left side lead, a little more movement for outside partner, and even more to cause one foot to cross the path of the other which results in a lock step. The shoulder section is primarily the "frame" that keeps the four-legged animal together. As you create more and more "shape" the frame (rib cage section) will follow slightly but will be much less than the hip section. The follower can feel this separated movement through the "frame". This timing of the shaping is critical to get the desired results. For example: in a forward lock step there is a little shape to prepare to step outside partner, a little more to actually step outside and more to cause the lock. Now we have to use a little less shape to "unlock". If you maintain the locking shape you partner will continue to lock.
Let's look at American Style Viennese Waltz. The goal of taking forward and backward steps is to have your legs move forward and backward from your hips (not out to the side). I start a Left Turn facing diagonal wall but I want to step down line of dance. In order to do this and still step straight back from my hips I need to create a separation. The separation is from the hip sockets to the ankle. I can move my hips easily 45 degrees by turning through the muscles in my supporting leg. So if I feel like I am screwing into the floor as I take the step I can comfortably step down line of dance. When I dance Viennese Waltz I create turn by three methods: 1 - turning through the supporting leg 2 - foot placement and 3 - ever so slight foot swivel. Again the timing of the application of these turning actions is critical.
I hope I have given you a little glimpse of what body separation causing shape is all about.