A persistence framework moves transient program data in its most natural form to and from a permanent data store. The permanent data store is in this case a relational database, and the natural form for program data is as in-memory objects. The persistence framework takes care of managing the database, and mapping between the database and the objects.

In short, a persistence framework can save you from writing a lot of boring and thus error-prone boiler-plate code. Most such frameworks require you to maintain lots of meta-data describing how to map the object data into the relational database, however, with the advent of advanced language features (i.e. reflection) most of this meta-data can be obtained at runtime.

You might want to check it out.