In a slot machine, whenever you hit a winning pay line; a payout is made, and that's it. It's time for another spin. At a tumbling (cascading) reel slot, all the winning symbols disappear, and those on top of them fall to the bottom filling in their slot. New symbols appear on top filling all void spaces. Think of it as a mini spin where you can theoretically have infinite winnings just like in Candy Crush and its clones.