The selection is pretty small to start: only Duolingo, Evernote, Sight Words, and Vine are on offer. As the screenshot above shows, those apps run inside windows much like Chrome OS's web apps, and they can sync data with actual Android devices. A special runtime called the App Runtime for Chrome (which, incidentally, is still in beta) makes the magic possible.
Google says more Android apps will make their way to Chromebooks over the "coming months." The company demoed Flipboard on Chrome OS back in June, so that app may be included in the next batch.