It is basically where you create your center of gravity I personally feel.
Some people carry it too high, up at their sternum. It belongs about 2-3 fiber widths above and below the belly button. The task of finding it and connecting to your partner with it is easiest using mental imagery.
Yep! Then comes the confusion between center of gravity and the active centers!
Women carry their center of gravity around the hips, and men carry it around the rib-cage. The structural development difference gives that away.
I think putting, "more weight into the floor", is a band-aid to fix something else that is seriously wrong somewhere else. Most teachers have no idea what's causing it, so they tell you to apply foot pressure and all sorts of horrible things that'll damage your feet, make you lose toenails, give you bone spurs, bunions, whatnots.
If you hear, "more weight into the floor", or anything of that sort, run away: this teacher can recognize pieces of the puzzle, but has no idea how to fit them together. This could end up damaging your body, sometimes irreparably, or worse: make your dancing feel bad!