Chrome OS has been able to run Android apps on compatible hardware for some time now, but code recently found in the Chromium repository, already present in the beta build of version 64, points to Chrome OS gaining the ability to run Android apps in the background. This behavior stands to bring Chrome OS more in line with what users would expect from a desktop OS, coming from any other type of laptop or desktop; Microsoft Windows, Apple Mac OS, and every flavor of desktop Linux all have simultaneous multitasking capabilities. While this can already be done in Chrome OS with native and web apps, bringing Android apps into the fold will significantly extend Chrome OS' functionality as a proper productivity OS.
The feature is fairly simple in its execution; on all Chrome OS devices, you can run multiple Android apps side by side. The complication is that clicking out of an Android app will pause that window, which means that music and videos will stop playing, and games will pause. This new feature forgoes this behavior, and allows Android apps to run in parallel, as the name suggests. To turn the feature on, simply go into your Chromebook's settings, so long as you're running Chrome OS version 64 beta or higher, and go into the Play Store settings to turn this feature on. Once you do, you'll be able to run Chrome OS and Android apps alongside one another, with none of them stopping.
The fact that this makes things less jarring for people switching from other desktop operating systems is a big part of the appeal of this new feature, and the potential use cases are vast, especially if a user rigs up multiple displays. Running a touchscreen drum Android app and a touchscreen piano Android app at the same time to record music in real time is one potential use, or perhaps watching a video tutorial for a game in one window while playing the game in another. The feature seems ready for prime time, but there's no guarantee that the new behavior will make it into the stable version of Chrome OS 64 when it drops.