Spring Beans Factory Model

         /*   Can You please help me? I have just started Spring.

            I know about Singleton and prototype but there is third one also . The third is Factory model . The sample code is: 
        */
             package com.springinaction.springidol;
            public classStage{
            private Stage(){
            }
            private static classStageSingletonHolder{
            staticStageinstance=newStage();
            }
            public staticStagegetInstance(){
            returnStageSingletonHolder.instance;
            }
            }
   /*         
       // XML is 

            <bean id="theStage"
        class="com.springinaction.springidol.Stage"
        factory-method="getInstance" />

*/

/* Please tell what is different between Factory model and singleton and prototype . And when I will use factory model and why?????*/