The "Store" function will swap your current piece with the next piece.
"Storyline" I made up: In the tetromino factory, The tetromino machine has gone haywire and has started producing strange new tetromino pieces, which are fusions of pre-existing ones. With the new store-o-tron and the new pieces, it's time to fight fire (aka the new pieces) with fire (aka the new pieces).. Or not.