Google FCM push messaging - How does Android OS identify my app to forward push notification to the app

[Isaac Newton]

I am configuring push notification functionality in my Android app using Google FCM. I would like to understand how is push message routed within the device after it reaches the Android OS. Does Android OS use the registration token (described here: https://firebase.google.com/docs/cloud-messaging/manage-tokens) to identify my app and forward the message to the app, or does it instead rely on the unique application ID (the application package name, like com.example.myapp) (https://developer.android.com/studio/build/configure-app-module#set_the_application_id). In case it's based on the application ID, should my notification also contain the application ID (app package name)? Thank you in advance!