The publish-subscribe pattern, which is sometimes referred to as pub/sub for short, is a messaging pattern that provides a way for a sender (publisher) to broadcast a message to interested parties (subscribers).
Rather than publishers sending messages directly to specific receivers as in the point-to-point channel pattern, the messages can be sent without any knowledge of the subscribers or even if there are no subscribers. Similarly, it allows subscribers to show interest in a particular message without any knowledge of the publishers or even if there are no publishers.