Do you mean the difference between an Enterprise
Java Bean and a class?
If yes, here's Sun's definition for Enterprise Java Beans:
"The Enterprise JavaBeans architecture is a component architecture for the development and deployment of component-based distributed business applications. Applications written using the Enterprise JavaBeans architecture are scalable, transactional, and multi-user secure. These applications may be written once, and then deployed on any server platform that supports the Enterprise JavaBeans specification."