He's just talking about Peach's ground floating technique which also happens to extend to Tails, Ganondorf, Mewtwo, Goku, and whoever else can float in Crusade I may be forgetting. I'm not sure how practical it may be for these other characters, but I digress.
Here's the page on the Smash wiki on the subject. Many of its uses are detailed here.
It's a crucial and famous technique used by every Melee Peach player, so I'm surprised you haven't heard of it.