Hi sureshbob, You can either use JSF along with Struts or only JSF or only Struts.
It can be say, all navigations can be done using struts and bean management can be done using JSF. JSF provide better controller facility and Event based navigation to your web pages. You can use event handling similar to what we do in Swing. And it has got features to create custom components, where you can define your own event handling and display features and provide navigation rules. Using JSF its easy to develop web applications. Many of the components are readly available with different JSF implimentations. So its not just changing the tag from html:Text to <h:inputText value=""/> you can go further by defining your actions and navigations in JSF.
The main philosophy behind JSF is Rapid Application Development(RAD). You can build web applications in minimum effort.
The struts-config is not required if you completly rely on JSF. JSF has similar config file called faces-cofig where you can specify almost all that features struts provides.