This, as far as I know is only useable on jigglypuff.
so, if you use
side B, pound, you travel a short distance.
this distance is the same in the air, as it is on the ground.
However, if you use pound just as you are landing on the ground, you will travel a lot further.
this reminds me of a wavedash effect, but the pound animation is streched out.
I don't know if this has been discovered, or if it was intentional etc. etc., but i thought it'd be kinda cool to share.
Again, I have not tested other characters, but I know that this works for