NHibernate-NPA is an implementation based on NHiberate for the NPA (.NET Persistence API) platform.
NPersistence (NPA) is a set of APIs that standardize Object Relational Mapping (ORM) throughout the industry. It allows an interface between .Net applications and ORM providers.
NHibernate is an Object Relational Mapping (ORM) provider. It allows to interact with a database such as Oracle, DB2, SQL Server or MySQL which are relational databases. Object Relational Mapping (ORM) tools map the bridges between the data representation in the relational database (as tables and records) and the representation in the .NET application (as classes and objects).
The NHibernate-NPA application is the bridge between NPersistence and NHibernate. It allows application to use NPersistence and have the NHibernate implementation of NPersistence.