NOTIFICATION API
The Notifications API lets a web page or app send notifications that are displayed outside the page at the system level; this lets web apps send information to a user even if the application is idle or in the background. This article looks at the basics of using this API in your own apps.
https://developer.mozilla.org/en-US/docs/Web/API/Notifications_API/Using_the_Notifications_API
PUSH API
The Push API gives web applications the ability to receive messages pushed to them from a server, whether or not the web app is in the foreground, or even currently loaded, on a user agent. This lets developers deliver asynchronous notifications and updates to users that opt in, resulting in better engagement with timely new content.
https://developer.mozilla.org/en/docs/Web/API/Push_API
Check these links for more info:
https://www.w3.org/TR/push-api/
https://www.w3.org/TR/notifications/