This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Are we talking about EJBs? If so then the answer the interviewer was looking for was Session Beans and Entity Beans. However, there is a third type that was added in EJB 2.0: Message Driven Beans. For more information, consult Dr. Google or see Sun's J2EE Tutorial.