A message broker is a software application that facilitates communication between different systems or services by managing the exchange of messages. It acts as an intermediary, ensuring that messages sent from one application are delivered to the appropriate destination, even if the systems use different protocols or formats. This helps decouple the components of a system, allowing them to operate independently and scale more easily. Message brokers often support various messaging patterns, such as publish/subscribe and point-to-point. Popular examples of message brokers include RabbitMQ, Apache Kafka, and ActiveMQ. By using a message broker, organizations can improve the reliability and efficiency of their data exchange processes.