The EJB 2.0 Specification defines JMS support through a new
type of enterprise bean, the message-driven bean. A
message-driven bean is invoked by the EJB container as the
result of the arrival of a JMS message. To a client, the
message-driven bean is a JMS consumer that implements some
business logic on the server. Clients communicate with
message-driven beans by sending messages to a JMS
Destination (either a Queue or a Topic) for which the
message-driven bean is a MessageListener. 

Message driven beans are distinct from both Entity and
Session beans. They have neither home nor remote interfaces.
Instead, they implement the javax.jms.MessageListener
interface.