The document presents an overview of enterprise service bus (ESB) technologies and concepts. It lists popular ESB products from vendors like IBM, Tibco, Oracle, Sonic and Microsoft. It then defines ESB as a modular architecture for designing and implementing interaction between software applications in a service-oriented architecture (SOA). Key functions of an ESB are listed as mediation, routing, transformation, orchestration and conversion. Finally, it distinguishes between enterprise application business logic and connectivity logic.