Windows Phone Frame and Page Navigation

Windows phone apps are based on the Silverlight page model where users can navigate forward through content screens . Using the hardware back button, users can easily navigate backwards.

The core elements of the page UI are a top-level container control named PhoneApplicationFrame which can host a PhoneApplicationPage. These are analogous to the standard  Frame and Page types, although you are required to use only the PhoneApplicationFrame and PhoneApplicationPage types in Windows Phone applications.
The PhoneApplicationFrame control holds contains the page control and other elements such as the system tray and application bar. The PhoneApplicationPage control holds the section of content for the application. There is only one frame allowed per Windows Phone application, but there are typicallyseveral pages of content which can be navigated to using the frame.