By default, buttons and other controls that cause a postback on an ASP.NET Web page submit the page back to itself. This is part of the round-trip cycle that ASP.NET Web pages go through as part of their normal processing. For details, see Introduction to Programming ASP.NET Web Pages.
Under some circumstances, you might want to post one page to another page. For example, you might be creating a multi-page form that collects different information on each page. In that case, you can configure certain controls (those that implement the IButtonControl interface, such as the Button control) on the page to post to a different target page. This is referred to as cross-page posting. Cross-page posting provides some advantages over using the Transfer method to redirect to another page