This is not exactly a new feature as Bubbles was included within the first beta version. However, Google explains that the latest beta version now provides platform support for Bubbles.
This is important as it highlights how Google is trying to get app-makers on board with the new feature at the app level without having to build out their own solution. Consistency of experience is the key here.
Google is positioning this as a feature that's built "on top of Android's notification system" and is expected to not only be easier to implement by developers, but also familiar.
As for what it does, many will already be accustomed to the experience as it seems like Bubbles will not be that different to similar features offered by third-party apps and services, including Facebook. The idea being users can continue to engage with features of an app without having to actually launch the app.
This naturally seems most likely to be of benefit to the messaging world and where it will draw the most comparisons to Facebook Messenger's solution. As regardless of the app, as long as the feature is supported users will be able to continue their messaging conversations while doing other things on their Android Q-running device.
Responding to messages is only one example of the type of use-case as in principle the options are relatively endless for how app-makers could include the support. For example, the announcement goes on to explain how Bubbles could prove useful for quick access to notes or translations, or for viewing current tasks.
Google states the overall end goal with Bubbles is to "make interactions consistent, safeguard user privacy, reduce development time, and drive innovation."
At present, this is all theoretical and even the support announced today is just more of a heads up as none of the apps will be using the feature in the current version of Android Q. Instead, this will be of most use for developers to know so they can prepare their apps to make use of the feature.
This shouldn't be too disheartening to Android users now though as Android Q itself is currently in a developer state and a fair amount away from being ready for general consumer use. There's plenty of preview versions set to become available before then and that means there's equally plenty of time for the feature to gain traction at the app level.
Presumably, this will be spearheaded by Google itself as it would seem logical Bubbles support will be showcased with Google's apps in an upcoming release. Therefore, the more tied in a user is to Google's services, the more likely they can expect to see the Bubbles end product in action soon.
Based on the current Android release, this is not something that all Android device owners that upgrade to Android Q will have to use – as there is the option to toggle the feature on and off within the settings.