Sometimes content is just best accessed in its native app. But just as often, we have no need for that app beyond a single specific instance. To deal with this inefficiency, Google is introducing Android Instant Apps. For content that is deep-linked into participating apps, the app will seamlessly download and install to let you use it in that very moment.
The key to this working out, said Google's Ellie Powers, is having participating apps be built with modules. Depending on what it is the user is trying to access, only the necessary modules of the full app are downloaded, making everything faster and less data-intensive.
And before we get to some examples, the big news is that this is not an Android N-exclusive feature. It will be backwards compatible through Jelly Bean,
presumably through updates to Google Play Services. Edit: Newly-posted developer documentation confirms that this is running on Play Services.
An example use case presented at I/O is being sent a video hosted at Buzzfeed. There's an app for that, but chances are you don't have it. With Instant Apps implemented, you just tap the link and within seconds a seemingly full version of Buzzfeed's app is opened for you to watch the video. I say "seemingly" because by all appearances it does everything the app needs to do, but modules that aren't necessary for streaming this video are left behind.
In the images above, you can see yet another example. She searches for a camera bag, sees one in the Google search at B&H Photo, and clicks like we all would do. But with Instant Apps, the "window" that opens is actually the Instant App for B&H. She looks at product info, adds it to her cart, and checks out with Android Pay.
Transactions are an interesting use, especially with Android Pay, because you are less likely to be dealing with security vulnerabilities in a native app as compared to entering payment info in a browser window.
Despite the polished demonstrations, Powers gave this fall as an arrival date, so it will be a little while before Instant Apps are ready for showtime.
Google has posted some official documentation about Instant Apps.
They have listed BuzzFeed, B&H, Medium, Hotel Tonight, Zumper, and Disney as early partners in the development of Instant Apps but say they soon will be expanding access. Developers can request early access through the link to the developers website.
Also, cool GIFs!
Google's Android Developers YouTube channel has posted a 4-minute video with more technical info.