In JSF 2.0, Facelets is the default View Declaration Language (VDL) instead of JSP. As a result, you don’t need to configure a view handler as you did in JSF 1.2. Facelets is a Java-Server Faces–centric view technology.
Facelets is based on compositions. A composition defines a JSF user interface (
UI) component structure in a Facelets page. A Facelets application may consist of compositions defined in different Facelets pages and run as an application.
Facelets is a templating framework similar to Tiles. The advantage of Facelets over Tiles is that JSF
UIComponents are pre-integrated with Facelets, and Facelets does not require a Facelets configuration file as Tiles does a Tiles configuration file.
JSF validators ...