As of now, we know hibernate as object relation mapping (ORM) open source framework. A framework, that eases our life in interaction with database, it not only supports many databases, but also provides a robust framework for connections and other complex data operations.  It supports persistent data store interactions in both Java and .NET technologies in object oriented way.
As J2EE moved to JEE 5, it introduced ORM into it’s technology specification through Java Persistent API (JPA). This means, we have a specification that defines the rules of object relation mapping …

Introduction to ORM concepts:
Object Relational Mapping is mapping of objects to tables in a relational database.