Immediate=true VS immediate=false in JSF Component

I was reading Core JavaServer Faces 开发者_StackOverflow社区and I was working on Event Handling. It says that if immediate=true for a component(lets say for a button), when we click that button, the process validation, and invoke application faces of the JSF life cycle will be done early. What does it mean? Can any body explain to me what the immediate=true will affect in each phases? I am confused.

Thank you.

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The following link most clearly demonstrates the JSF Lifecycle Phases, How to Debug them, and how immediate=true affects this.

http://balusc.blogspot.com/2006/09/debug-jsf-lifecycle.html#AddImmediateTrueToUIInputOnly