In November 2015, Google prototyped app streaming on a few select apps. It now seems to be available for many apps in the Google mobile search results.
The same requirements apply: You must be running Android L or greater and must be on WiFi when you do your search within the Google Search App. Then, if you see an app come up, it may have a button next to the green “Install” button that says, “Try Now.” When you click on the “Try Now” button, the app streaming happens right on your device — in real time.
App streaming lets you try an app without installing the app to your device.