JPA is JSR i.e. Java Specification Requirement to implement Object Relational Mapping which has got no specific code for its implementation. It defines certain set of rules for for accessing, persisting and managing the data between Java objects and the relational databaseWith its introduction, EJB was replaced as It was criticized for being heavyweight by the Java developer community.
Hibernate is one of the way JPA can be implemented using te guidelines.Hibernate is a high-performance Object/Relational persistence and query service which is licensed under the open source GNU Lesser General Public License (LGPL) .The benefit of this is that you can swap out Hibernate's implementation of JPA for another implementation of the JPA specification. When you use straight Hibernate you are locking into the implementation because other ORMs may use different methods/configurations and annotations, therefore you cannot just switch over to another ORM.
