Triggers functionality

when is the triggers functionality to be used? when isAsyncPostBackTrigger andPostBackTrigger used? what does their arguments mean?

You can use thePostBackTrigger to specify a control inside the UpdatePanel that should do a postback (not a asynchronous postback.)

You use theAsyncPostBackTrigger to define a control and optional event of the control that should do a asynchronous postback and refresh the UpdatePanel. You can for example use theAsyncPostBackTrigger when you have controls outside of the panel and want them to refresh the panel.