The Android App Bundle (AAB) is a publishing format that includes all an app's compiled code and resources, which are then deferred to Google Play for APK generation and signing. This allows only the necessary code and resources to be downloaded to run the app on specific device configurations. Firebase App Distribution makes it easy to distribute your app to testers, allowing you to get feedback early and often. It integrates with Google Play's internal app sharing service to streamline testing and launching processes. fastlane is an open-source platform that simplifies Android and iOS deployment, automating every aspect of the development and release workflow. With fastlane, developers can save hours by automating tasks, integrate with over 400 tools and services, offer easy setup, and support multiple platforms including Flutter. To get started with fastlane, developers need to install Ruby on their machine and initialize it in their app using a command, then add the App Distribution plugin to automate distribution tasks.