Yugioh Generation Force is the first booster set to have the new 4th Generation of Yu-Gi-Oh! monsters: the easy-to-play Xyz Monsters! (pronounced ik-seez!)
The first 3 Generations of Yu-Gi-Oh! monsters were Fusion Monsters, Contact Fusions, and Synchro Monsters. Xyz Monsters bring your Deck some 4th Generation power, because the 4th way to Summon from your Extra Deck is the easiest one yet! Plus they automatically work with ALL the monsters you already have in your Deck. No adjustments required!