The Android Bundle ID is a unique identifier for your app in the Google Play Store. You’ll need it when setting up things like Firebase (which is used for push notifications) or publishing your app to Google Play.
When publishing, you'll need to copy the Android Bundle ID from Buildfire and paste it into the Google Play Console.
How to locate your Android Bundle ID
Log in, go to Settings in the left navigation, select Integrations
Under the Certificates tab, scroll down to the Google Services (Android) Android Bundle ID
Copy the value—it will look something like www.numbersandletters.com