Gimmicked deck lets you force a card with no skill necessary.
50-50 deck means half of the cards are the same card, and the other half are all different cards. By keeping all the same cards at the top half of the deck, and forcing your spectator to choose from that half, you force the spectator to choose a specific card (the card that makes up half the deck).
The deck shown in the photo forces the 8 of Spades; you will probably get a different force card, but the deck works the same way.
