Stateless session bean: It remains for a very short period of time. It is used when there is no need of worry of the state of the specific client. Validation of the credit card is a good example of the Stateless session beam.
Stateful session beam: It has the unique feature which is absent in other beams that it can be implemented in the web whiles other cannot. It is used to maintain the conversation between the client. It saves the instance of conversation in the area like the hard disk before its proceeding into a passive state. Whenever the same client sends a request instance to come back to its original place (main memory). Online transaction, Online reservations are some examples of the Stateful session bean.