Google is improving both app discovery in the Play store and seeking to increase usage of the apps you already own via an update to search on Android handsets.
Whether people are using the Google Search app, or searching on the Chrome or Android browser, results will now include information from apps that have already been downloaded, as well as relevant results from the Play store.The results include a direct click to open or click to download command.
Google's App Index was announced as part of Android 4.4 KitKat. Apps already using it include Etsy, OpenTable and Wikipedia, and many more devs will follow if they want to take advantage of this added prominence.
From the information we've seen, it looks like app search may be prioritised over the mobile web. Google said they could not comment on the priority given to paid and natural web search on mobile compared to the new app function, or whether apps would now be open to paid opportunities.