Hibernate - how does it handle changes in a ManyToMany relationship?

Lets say that I am creating some EJB entity beans that are persisted via Hibernate.  One bean can contain a list of the other type of bean - bean.getList() and bean.setList(theList).  (the list contains a list of a different object.)  The relationship between the two tables that the entities map to, in a third table, which just has the ID's from the other two.  (Basically, this allows for a many to many relationship.)

If I add or remove things from that list on a web page, how does Hibernate handle updating the table?  Since things could be both added and removed, I am curious how Hibernate handles this behind the scenes?  Does it first determine what it needs to change, and then updates those things?  Would it handle something like that correctly?