The Entity Bean is directly interacting with the database.
AS and when new transactions are made they are recordeed in
the database to take care of persistence. 

In case of session beans all transactions are maintained in
a session. It is not necessary that the user has to submit
these trasnactions to the DB. The user may choose not to
submit them and the trtasnactiosn in the session will be
lost. This can also occur whe the user closes the browser
without submitting or when the session expires due to a time
out.