The app lets you browse Khan Academy's huge collection of educational videos and explanations on various topics ranging from math to science, history, economics, art, and more. Find something you want to study later on, while you're in the subway for example? You can bookmark it to be saved and available offline to you. And everything you do is synced between the app and the website. However, the app doesn't have the website's cool exercises that help you better understand each subject matter. I guess they gotta leave something for future versions.
The app is available for free on the Play Store or you can grab it on APK Mirror. The Google+ community is still live if you want to stay on top of the latest beta improvements to the app before they make it to the public release.