Persistence refers to the ability to store objects in a database and use those objects with transactional integrity. In a J2EE application, data is typically stored and persisted in the data tier, in a relational database.
Entity beans are enterprise beans that contain persistent data and that can be saved in various persistent data stores. The entity beans represent data from a database; each entity bean carries its own identity. Entity beans can be deployed using application-managed persistence or container-managed persistence.