Legendary monster Xerneas (the cover star or Pokemon X) is a Fairy-type Pokemon with an ability called Fairy Aura which powers up Fairy-type moves. It also has a special move called Geo Control.
Meanwhile, Yveltal (the Pokemon Y cover star) is a Dark/Flying-type Pokemon with the Dark Aura ability. This powers up Dark-type moves. It also has a special move called Death Wing.
Nintendo has confirmed a worldwide Pokemon X & Y release date of October 12.
A recent Pokemon X & Y gameplay trailer showed off new battle footage and player customisation options.