Xbox One Achievements will be split into two types - achievements and challenges - and offer new kinds of rewards, including extra game content such as maps, characters and stat boosts.
Other Xbox One applications will also be able to use Achievements to give you things like sneak peek content, early access or subscription extensions, explained Xbox Live Achievements program manager Cierra McDonald.
It isn't clear whether you can actually earn Achievements for watching films and playing music, but it sounds to me like other Xbox One applications are only involved with Achievement rewards.
Only game achievements (lower-case - a specific type of Achievement) will award you Gamerscore, though. This is still "a critical part of the Xbox gaming experience", McDonald wrote, reiterating that Gamerscore will carry across from Xbox 360 to Xbox One.
Both achievements and challenges are "officially" considered Xbox Live Achievements so they share characteristics. You unlock them and they're saved to your Achievement history, where they're illustrated with a pretty - "more beautiful" - icon.
They're "often" - not always - associated with the Xbox One video recorder (DVR), so they can capture the moment of Achievement. (Is associating an Achievement with the DVR a dev's decision, then?)
Challenges differ in that they're time-limited but can also be shared across different games and earned by multiple people - communities.
"Imagine, for example, a game releases a headshot weekend challenge that requires players to cumulatively headshot 1 million baddies in a three-day period. And every person who participates and meets the challenge's goals gets the unlock on his or her Achievement history and reaps its reward," McDonald explained.
There's no Gamerscore awarded for challenges because challenges expire, which wouldn't be fair on Sally and Jim who were on holiday when the challenge was added, for instance. Not that Gamerscore actually means anything at present - though perhaps that will change with the new system.
Xbox One Achievements are cloud-powered so they're less rigorously nailed to a game upon release, which is why challenges can be cross-game and involve multiple people. It also means developers can add new achievements to existing games and not have to bung them in paid DLC. You'll save money and developers will be able to react to how the community is playing a game.
Finally, the Xbox One dashboard apparently "greatly improves" how you discover and view Achievements, and will present you with progression data outside of - and before - you launch a game. You'll be able to see how your Xbox One Friends are getting on as well.