Microsoft has overhauled the Achievements system, adding a second tier of non-Gamerscore affective challenges among other changes.
The changes are designed to ensure developers can "deliver more interesting, complex, and fulfilling goals and rewards to you", Xbox Live Achievements program manager Cierra McDonald wrote in a lengthy post on Major Nelson's blog.
First of all, video and music apps can now offer Achievements - however, they won't be able to give you any Gamerscore.
Instead, they'll be able to offer you various bonuses and rewards,. Across video, music and games, these rewards could include digital artwork, new maps, characters, temporary stat boosts, sneak peek content, early access, or subscription extensions.
Confusingly, (upper case A) Achievements now come in two categories - challenges and (lower case a) achievements.
An achievement is available from the game's launch and can be completed at any time - barring those ties to multiplayer, which will become unavailable if a game's servers are taken down. It offers Gamerscore and possibly other rewards. McDonal described it as a "promise" - meet the conditions and you get the reward, on your schedule.
A challenge, on the other hand, is an "opportunity". It also sets a goal and offers a reward, but it must be completed in a certain time frame, and cannot affect your Gamerscore. Challenges may be set for a community rather than individual players, like reaching so many million kills over the course of a week, and they may span multiple titles.
Both appear in your Achievements list with an icon, and may include a DVR capture of the moment you unlocked it.
Both kinds of Achievement are now managed from the cloud, and that means developers can add more after launch - so you have a chance to increase your Gamerscore without buying DLC or applying patches. It also means developers can plot reactionary challenges, or hold competitions asking players to design them.