What is the difference between a session and a transaction in JPA 2.0?

Question

I just begin my JPA 2.0 studies, and I have this piece of code:

em = SessionFactory.startSession();
tx = em.getTransaction();

My problem is

Answer 1

em = SessionFactory.startSession();

In JPA, there is no Session and no SessionFactory. SessionFactory is a hibernate-specific interface that you shouldn't use if you use JPA (use either Hibernate's own API or use Hibernate as JPA Provider, but not both.)