Creating notifications is very straightforward -- you simply use the Firebase Notifications GUI in the console to compose and send notifications to apps that are linked to your project in the console. When your app is in the background on a user's device, notifications are delivered to the system tray.

How does FCM notification work?

The Android push notifications through FCM actually treats the Data Messages as notification messages itself. As the interactions in the data messages are handled by the app itself, FCM's work is just to deliver a notification and the message content. ... A Mobile app. Connection to the FCM server.

How does firebase push notification work internally?

The Android system looks at the message to determine which app it's for, and starts that app. The app must have registered with Android to use GCM, and it must have the relevant permission. When the app starts, it might create a notification straight away with the data from the message.