Bringing more powerful apps to Chrome OS is a great idea. Making it easier to bring mobile apps to Chrome encourages developers to go beyond web apps and write native apps that work offline, include hardware integration and work outside of the browser. While cross-platform web apps are still useful, the new Chrome apps can bring some missing features that people expect to find in native apps. "These combine the best of websites and native applications — they're available offline, are always up to date, and they can communicate with devices like USB drives & Bluetooth speakers," explains Google.
"These first apps are the result of a project called the App Runtime for Chrome (Beta), which we announced earlier this summer at Google I/O. Over the coming months, we'll be working with a select group of Android developers to add more of your favorite apps so you'll have a more seamless experience across your Android phone and Chromebook," informs Google. You can tell Google what Android apps you'd like to be ported to Chrome.
For now, the first 4 apps can only be installed in Chrome OS, but I'm sure that Google will add support for Chrome in the near future.
It's interesting to notice that the apps aren't manually ported to Chrome, as I assumed. Here's an explanation from a Google employee:
"The app code is all running on top of the Chrome platform, specifically inside of Native Client. In this way the ARC (Android Runtime for Chrome) apps run in the same environment as other apps you can download from the Chrome Web Store, even though they are written on top of standard Android APIs. The developers do not need to port or modify their code, though they often choose to improve it to work well with the Chromebook form factor (keyboard, touchpad, optional touchscreen, etc)."
Here's an APK for Duolingo (Android app) inside the CRX file (Chrome app):