Is an ESB the same thing as SOA? Not exactly. An ESB does not provide a Service Oriented Architecture, but it does provide the tools than can be used to build one—especially loose-coupling and asynchronous message passing. SOA is a series of principles, patterns, and best practices. JBoss ESB is the base SOA infrastructure that JBoss has contributed to the community which can be used to develop SOA applications.

In middleware, one of the most powerful approaches is SOA based on an ESB. In order to integrate enterprise software applications developed at different times, by different organizations, and even communicating via different protocols, you don't have to rewrite them to speak one consistent language. JBoss ESB enables you to "plug" these applications as services into the bus. JBoss ESB takes care of transforming messages between the protocols and routing the messages to the correct services.