From the YouTube video description itself:
"Coming June 23, 2015, Batman: Arkham Knight is the epic conclusion to the Rocksteady Batman: Arkham Trilogy.
For the first time ever, watch Batman: Arkham Knight’s exciting new “Dual Play” mechanic in action as you switch seamlessly between The Dark Knight and his allies including Robin, Nightwing, and Catwoman in free-flow combat.
With his back against the wall, Batman turns to his closest allies to help him save Gotham City from the clutches of Scarecrow and the Arkham Knight’s army. A familiar face also returns to give The Dark Knight a message he cannot ignore…"