How is the use of Servlet different with JSF Facelets as compared to JSP

How is the use of Servlet different with JSF Facelets as compared to JSP

can someone please explain to me how the servlet class works with the JSP
as compared to the JSF facelets.
I know that the servlet class processes the HTTP request and response from
the view page to the Java bean. But there is also the issue of
servletFaces mapping when you read the facelets documentation.
Am quite new to JEE therefore will be glad for better explanation.