1. Session Beans, it is also sub divide into two forms
Stateless Session beans
Stateful Session Beans
2. Entity Beans
3. Message Driven Beans or they are also called Message Beans.
Now I will explain them one by one:
Session Bean is created by a customer and its duration is only for the signal client server session. The function performed by this bean is calculations or database access, for the client. This bean can be transactional, because it is not recoverable and due to this may a system crash can occur. Its object is to manage its own unrelenting data.The stateless Session Beans is distributed object which has no connection with informal state; only allow parallel access to beans.Now the Stateful Session Bean has a connection with informal state, but its access is very limited to the customer.The second types are called Entity Bean and its function is to database the unrelenting data. It is recognized by a main key, if the container which is hosted by entity bean crashes, it will destroy the remote reference.Message bean is similar to session bean, except it responds to java message service.