Clients cant make requests to servlets that dont exist. A web application typically comprises of servlets and JSPs. Add some EJBs to that equation and you get an application that delegates the work of business logic to the EJBs. Now you have an enterprise application (which need not be confined to the concept of EJBs alone).
You can still have a web server that will service EJB clients even if you dont use servlets and JSPs. That means that you are not using the web container part of the web server where you would usually host your servlets and JSPs.