From the website:
Relational Persistence for Java and .NET
Historically, Hibernate facilitated the storage and retrieval of Java domain objects via Object/Relational Mapping. Today, Hibernate is a collection of related projects enabling developers to utilize POJO-style domain models in their applications in ways extending well beyond Object/Relational Mapping.
Interesting factoid from the documentation:
A RDBMS defines exactly one notion of ‘sameness’: the primary key. Java, however, defines both object identity (a==b) and object equality (a.equals(b)).
Unfortunately, neither an RDBMS nor Java define tests for the identity of the subjects they represent. Nor appear to realize that the structures in both are subjects in their own right.