Mule the leading open source ESB and integration platform

Mule is a messaging platform based on ideas from Enterprise Service Bus (ESB) architectures. An ESB works by acting as a sort of transit system for carrying data between applications within or outside your Intranet. The ESB defines a series of stops, or "endpoints", through which applications can send or receive data onto or from the system. The heart of the system, the messaging bus, is what routes messages between endpoints. The messaging backbone of the ESB is usually implemented using JMS, but any other message server implementation could be used, such as MSMQ, IBM MQ Series or Tibco Rendevouz.

Mule, in fact, goes beyond the typical definition of an ESB. We prefer to define Mule as a light-weight messaging framework that contains a distributable object broker for managing communication between applications. The point of the object broker is to manage service components. These components are called Universal Message Objects or UMOs, and are basically just plain old java objects (POJO). UMOs can exist in the same VM or can be scattered around your network and the Internet. The object broker itself follows a Staged Event Driven Architecture or SEDA design pattern. All communication between UMOs and other applications is made through message endpoints. These endpoints provide a simple and consistent interface to vastly disparate technologies such as JMS, SMTP, JDBC, TCP, HTTP, XMPP, file, etc.

Refer : http://mule.mulesource.org/display/MULE/Home

Start Using it, then you will feel the diffirence