Local stateless EJBs vs Remote

I'm kind of a newbie in EJBs,but I've been given an EJB tier to improve.
This tier consists of an EJB wich exposes the operations available:

@Stateless(name = "myejb")
public class Facade implements FacadeRemote
{
    @EJB
    private EntityAHomeLocal entityAHome;

    @EJB
    private EntityBHomeLocal entityBHome;

// methods signatures and implementations
}

As you can see this EJB use other local EJBs that manage operations on entities.

@Stateless
public class EntityAHome implements EntityAHomeLocal
{
    @PersistenceContext(name="myUnit")
    private EntityManager manager;


    // methods signatures and implementations
}

I'm having hard time to fully understand the architecture of this tier.

• Is this kind of architrcture common ?
• Are local stateless EJB managed throught a pool of instances just like remote stateless EJBs ?