Message Driven Bean(MDB) is follows the MOM architecture.There are lot of products available in market like IBM Websphere. MDB(producer) put the message(txt) in the Queue, later the consumer picks up the message when the client server up.Here will see Point to Point (P2P) example.
EJB is used to implement the business logic in server side. It is a Distributed Architecture, so from anywhere we can invoke the business logic using Remote Object.