JBoss Messaging is a high-performance, reliable, and scalable messaging platform that allows application components to communicate with each other using messages. It is an open-source, standards-based messaging system that provides features like message persistence, distribution, and transaction management. It is commonly used in enterprise-level applications to ensure reliable and timely communication between distributed components. Knowledge of JBoss Messaging is useful for developers, system administrators, and architects who work with messaging systems in Java-based applications.