Java Server Faces (JSF) is a web application framework that uses XHTML markup and allows building user interfaces for Java-based web applications. The document discusses the JSF architecture which follows the Model-View-Controller pattern and includes XHTML files, CSS/JavaScript resources, servlet configuration files, class files, and library files. It then provides an example of creating a simple JSF project to convert meters to inches that displays the result on screen after configuring JBoss and starting the application.