A message broker (wikipedia) is a component that is part of an IT infrastructure whose primarly goal is to receive messages and make them available to other components.
It is a way to decouple applications inside an information system and provide high performance.
- Apache Kafka goal is building real-time data pipeline and streaming apps
- Azure Service Bus is a multi-tenant cloud messaging service handling asynchronous operations
- RabbitMQ is an open source message broker, whose commercial version is managed by Pivotal Software