Amazon SNS is a web service for mobile and enterprise messaging that enables you to set up,operate, and send notifications.

Amazon SNS follows the publish-subscribe (pub-sub) messaging paradigm,with
notifications being delivered to clients using a push mechanismthat eliminates the need to check periodically (or poll) for new information and updates.

Amazon SNS consists of two types of clients: publishers and subscribers (sometimes known as producers and consumers). Publishers communicate to subscribers asynchronously by sending a message to a topic. A topic is simply a logical access point/communication channel that contains a list of subscribers and the methods used to communicate to them.

Diagram of topic delivery

Common Amazon SNS Scenarios

Amazon SNS can support a wide variety of needs, including monitoring applications,
workflow systems, time-sensitive information updates, mobile applications, and any other application that generates or consumes notifications.