How to make PUSH notifications for Android with pages?

On Facebook I noticed this feature: if you enable notification, the browser creates a gun, even if the site is closed. How to make a similar on your website?
July 2nd 19 at 14:13
2 answers
July 2nd 19 at 14:15
July 2nd 19 at 14:17
Time browser or the website to close, what to do in a browser?

https://firebase.google.com/docs/notifications/

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