App Downloads are conversions that are tracked when a user downloads or installs a mobile application for the first time.
Mobile app installs campaigns can help you create custom app install ads that run exclusively on phones and tablets. AdWords helps create your app install ads based on your app icon and reviews, and these ads take people straight to the app store to download your app. When a user downloads or installs a mobile app it’s considered as a conversion.
App installs: Conversion tracking can measure how effectively your ads are leading people to install your mobile apps. There are a couple of different ways to track this:
- Downloads from Google Play: For Android apps, you can track when someone who clicked your ad downloads your app from the Google Play store. Conversions are tracked automatically from Google Play, and you don’t need to add tracking code to your app.
- First opens: For both Android and iOS apps, you can track the first time someone who clicked your ad opens your app after installing it. You will use this option if you use Firebase, or if you use a third-party app analytics provider.
Read more here: https://support.google.com/adwords/answer/6100665