Every month, Microsoft adds new feature updates to the Xbox One platform, and an upcoming one is going to be a doozy: backwards compatibility with the Xbox 360. [Updated 7 August 2015.]

Update 7 August: At Gamescom 2015 Microsoft announced that from November all future Xbox One Games with Gold titles will be backwards-compatible at launch.

Speaking back in June at E3, Microsoft's Xbox chief, Phil Spencer, said: "Our goal is to deliver the largest games catalog ever on Xbox, and Xbox backwards compatibility allows us to do just that."

Mike Ybarra, head of the platform engineering team at Microsoft, said that the Microsoft will offer "hundreds of titles by the holiday season, with hundreds more in the months to come." Digital versions of your Xbox 360 titles will automatically begin showing up on Xbox One, he said.

Retails discs will work as well: "Put the disc in, download the game, and you're ready to go," Ybarra said.

Microsoft showed off Mass Effect running on the Xbox One, but with Xbox One features, such as the ability to take screenshots, broadcasting, game DVR, and even streaming via the Xbox app on Windows 10. You'll also be able to play multiplayer with your Xbox 360 friends.

And apparently all that's required is for the developer to sign off on it. "No work is required on their part to make all of this possible," Ybarra said.

If you're an Xbox Preview member, you're lucky--you'll get an initial set of titles try out today, Ybarra said. For everyone else, there's Christmas.

"For Xbox One, we won't charge you to play the games you already own," Ybarra said. That was obviously a dig at Sony, whose PlayStation Now service allows you to play PlayStation 3 games on your PlayStation 4 console, but charges you $20 per month for the service.

Why this matters:  Backwards compatibility was one feature that every Xbox One gamer hoped for, but no one actually expected. Now, any Xbox One owner can take advantage of their back catalog--or jump in to older games that they may have passed over. Game developers have to be excited--Microsoft just gave their Xbox 360 lineup a jumpstart, opening those older titles up to gamers who owned a PlayStation during that generation.