Usage of "include" or "forward" in Action definition

[James Howe]

Could someone explain a little more about when you would want to use either 
the "include" or "forward" attributes of the action tag (used in 
struts-config.xml) instead of the "type" attribute"?  An example or two 
would go a long way to clarifying when and why someone might want to use 
either include or forward.

Thanks.