how to load a page partially when button_click will fair

AsyncPostBackTrigger: Asynchronous Postback triggers update the page partially without refreshing the whole page (AJAX)
-Converts postbacks into async callbacks
-Typically used to trigger updates when controls outside an UpdatePanel post back If ChildrenAsTriggers="false", can be used to specify which controls inside UpdatePanel should call back rather than post-back

PostBackTrigger: Postback triggers update the complete page caused by complete post of the page to the server.
-Lets controls inside UpdatePanel post back
-Typically used to allow certain controls to post back when ChildrenAsTriggers="true"