Java language question: static classes ?

[peter . pilgrim]

     I was looking at the Kim Topley  "Core JFC" book particularly a 
     convenience class to swith the Swing/JFC PL&F (Chapter 13)
     the other day I found it was declared like ?
     
     protected static class SwitchPLAFClass {
               ~~~~~~~~~~~~
     
        private Frame f;
        private LookAndFeelInfo lfi
     
        ...
        
     }
     
     
     What is a static class?
     
     I am guessing it is sharable entity.
     
     Pete