Enterprise JavaBeans (EJBs) are reusable software components that can represent either business logic or data. There are two main types of EJBs - session beans which represent business logic and entity beans which represent and manipulate data. EJBs provide benefits like transaction management, security, and abstraction from technical details. They allow components to be reused across applications and systems. EJBs communicate using RMI over IIOP and can be accessed from various clients including other EJBs, servlets, JSPs and applications in any language that supports CORBA.