This section contains text from The Java Message Service Tutorial. Because message-driven beans rely on Java Message Service (JMS) technology, to fully understand how these beans work you should consult the tutorial at this URL:
A message-driven bean is an enterprise bean that allows J2EE applications to process messages asynchronously. It acts as a JMS message listener, which is similar to an event listener except that it receives messages instead of events. The messages may be sent by any J2EE component—an application client, another enterprise bean, or a Web component—or by a JMS application or system that does not use J2EE technology.