Google now shows a "Open in App" button in Google Search results which allows you to directly open deep linked content in your native Android app. This search feature is available on searches done using Google Search App version 2.8+ for Android 4.1+, and in mobile browsers on Android if the user is signed in.
App indexing does not impact on your website's ranking in the search results page. It does affect how a search result of your website is displayed, namely by adding a button to open the content in your app if the user has the app installed.
For example, imagine you run a recipe website and have an app that can also show your recipe. Thanks to the app indexing feature, when a Google searcher on a mobile device is shown one of your recipes as a search result, they will now be able to open that result directly in your app if they have it installed.
To enable this feature you need to configure both your website and your app to tell Google their relationship, by:
Once your Android app includes the right intent filters and your website includes the corresponding link elements as described above, it will be possible for Google algorithm to show the "Open in app" button when appropriate, thus helping users discover and enter your app's content directly from Google Search.
Learn more about how to add app deep links on your website and intent filters in your app manifest file that define how to reach specific content inside your app.