Today, you have seen common ways that EJBs are used in applications and why you would want to use them. You have seen that an EJB will have a home interface, a business or remote interface, and an implementation. You have seen how the EJB container will provide much of the underlying code to support the EJB, and that it relies on detailed deployment information that defines the EJB's requirements.
You have also seen that a J2EE application consists of components and deployment information and how the server-side part of such an application can be deployed. You have seen a client that is able to use such server-side components and the code required to write such a client.