Hibernate is a persistence engine in the form of a Framework. It loads business objects from a database and saves changes from those objects back to the database. As we mentioned above, it can load or save an entire object graph with just a line or two of code.
NHibernate uses mapping files to guide its translation from the database to business objects and back again. As an alternative, you can use attributes on classes and properties, instead of mapping files. To keep things as simple as possible, we're going to use mapping files in this article, rather than attributes. In addition, mapping files make for a cleaner separation between business logic and persistence code.
