Ahhh. Found the thread you asked me about I guess.
Basically, on your back, legs spread wide, weight on your shoulders and feet, so that you can lift your buttocks up off the floor or bed.
You do so in a manner that invites your dominant (or bed partner) to use you. You do so in a manner that shows you can be mounted and can actively pleasure your partner from the submissive position.
It will tighten your thighs, calves, as well as your butt. It will help your pelvic girdle. Combine it with kegels and you will become a tight cockmilking machine.
Phew... now I'm horny too!!
PS. For all intents and purposes, this is equivalent to the kajira position Sula-Ki (in case you want to look it up or find an illustration.)