Servlets and JSP are part of
Java EE (the
web tier part). EJB is another part of Java EE (the
business tier). Tomcat is a servlet container; it only supports servlets and JSP, not EJB. Weblogic, Websphere and JBoss also support EJB.
See
http://java.sun.com/javaee for more information, including tutorials, on Java EE.