JPA (Java Persistence API) defines an interface to persist normal Java objects (or POJO's in some peoples terminology) to a datastore. JPA is tightly coupled to RDBMS datastores and so is currently of no use when you require an alternative type of datastore (such as XML, OODBMS, etc). JPA is a standard approved in June 2006 as part of "EJB3" though can be used outside of the J2EE container. JPA defines the interface that an implementation has to implement. The whole point of having a standard interface is that users can, in principle, swap between implementations of JPA without changing their code.