Definition: a message broker is intermediary software that uses a formal message protocol for the publishing, queuing and consumption of message content.
IAM provides a robust, highly scalable message broker service. Decoupling applications and providing for information to be published once and consumed multiple times is required for successfully integrating disparate applications and preparing for applications yet to be developed. Application workloads can remain constant even as the demand for the application data greatly increases.
Developer resources, further reading: