What is EJB role in J2EE?

I have started working on EJB mainly because I wanted to use it mainly for J2EE, Please let me know the role of EJB in J2EE..

The EJB server provides an environment that supports the execution of applications developed using Enterprise JavaBeans (EJB) components. The custom SAF EJB role mapper allows an installation to map J2EE role names to SAF EJBRole profile names. It manages and coordinates the allocation of resources to the applications. Enterprise beans typically contain the business logic for a J2EE application.

The EJB server must provide one or more EJB containers. An EJB container manages the enterprise beans contained within it. The custom SAF role mapper is a Java-based exit to replace the EJBROLE class profile construction algorithm. The custom SAF role mapper is called to generate a profile for authorization and delegation requests. For each enterprise bean, the container is responsible for registering the object, providing a remote interface for the object, creating and destroying object instances, checking security for the object, managing the active state for the object, and coordinating distributed transactions.

Enterprise beans typically contain the business logic for a J2EE application.The EJB server must provide one or more EJB containers. You also can enable the role mapper by setting the custom property com.ibm.websphere.security. An EJB container manages the enterprise beans contained within it.