In the publish-subscribe messaging model, a publisher broadcasts the message and consumers who are subscribed can consume the message and carry out some operations on it. This model represents a one-to-many relationship. Here, the messages are logically associated using topics and the subscribers register with the message provider about specific topics. Whenever the publisher sends out relevant messages, the message provider that is maintaining the list of subscribers for that topic will notify and deliver the messages.

This is shown in the following diagram:

As depicted in the preceding diagram, the publisher broadcasts the message to a topic, and the subscribed consumers can consume the messages from there and process them further.

In this model, the messaging topic decouples the publisher and the subscriber of the message.