Azure Notification Hubs
While Event Hubs allow you to take in millions of events per second, Azure Notification Hubs send data in the other direction—they enable you to send push notifications to mobile devices from any backend, whether in the cloud or on-premises. With a single API call, you can target individual users or entire audience segments of millions of users across all of their devices.
Push notifications are challenging. In general, the app developer still has to do much of the work to implement even common push notification scenarios, like sending notifications to a specific group of customers. To make them work, you have to build infrastructure that is complicated and, in most cases, unrelated to the business logic for the app.
Notification Hubs remove that complexity, eliminating the need for you to manage the challenges of push notifications. Notification Hubs are cross-platform—they can be used to support Windows, iOS, Android, and Windows Phone apps; they reduce the amount of push-specific code you have to put in your backend. They are fully scalable, allowing you to send notifications to millions of devices with a single API call.
All of the functionality of a push infrastructure is implemented in Notification Hubs for you. The devices only have to register their PNS handles, and the backend can send messages to customers without worrying about the platform the customers are using.
Source of Information : Microsoft Azure Essentials Fundamentals of Azure Second Edition