How does firebase cloud messaging work?

Related questions

1. What is GCM FCM?
2. What is API key used for?
3. Is Geocoding API free?
4. What is a FCM token?
5. What is GCM key?
6. What is Gcm_sender_id?
7. What is API key in FCM?
8. What is a GCM ID?
9. What is the difference between information and message?
10. What is difference between information and data?

Tags

1. #server
2. #android
3. #build
4. #target
5. #firebase
6. #receives
7. #includes
8. #which
9. #components
10. #javascript
11. #receiving
12. #client
13. #cloud
14. #messages
15. #environment
16. #functions
17. #trusted
18. #sending
19. #implementation