The program allows gamers who pay for downloadable content on the Xbox 360 to get the same content for free on the Xbox One, for participating companies. Call of Duty: Ghosts and Battlefield 4 have already been confirmed as taking part in it. Ubisoft also has reportedly signed on as well.
"Season Pass Guarantee makes transitioning from Xbox 360 to Xbox One an easier and smoother process, so you don’t have to worry about which console you're playing games on or repurchasing your existing add-ons on Xbox One," Microsoft stated.
In other words, if you buy the Call of Duty: Ghosts Season Pass on the Xbox 360, when the player gets the Xbox One version, all of the DLC purchased on the 360 version will be available for free on the Xbox One. (Gamers in the US also have the bonus of GameStop offering $50 credit for gamers who want to trade in the Xbox 360 version of a game for the Xbox One version, meaning they're only paying $10 to update from 360 to One.)
Sony has not announced any such program - it'll be interesting to see if the publisher follows suit.