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EJB takes a high level approach for building distributed systems.

It frees the application developer to concentrate on programming only the business logic, while removing the need to write all the "plumbing" code that is required in any enterprise application development scenario. For example, the enterprise developer no longer needs to write code that handles transactional behavior, security, connection pooling or threading, because the architecture delegates this task to the server vendor.

The current version of EJB bears little relation to "plain old vanilla" JavaBeans. However, the name "Enterprise JavaBeans" implies a relationship that doesn't really hold. Typically, JavaBeans are used in a manner similar to Microsoft ActiveX components (to provide user-friendly code with user interfaces), whereas EJBs are used to implement transactional middleware and are decidedly non-visual. Additionally, EJB does not include things like BeanInfo classes, property editors, or customizers either.

for read more information:
http://www.idevresource.com/java/library/articles/server.asp