The following are definitions in the context of the app page model for Windows Phone:
Page: A user-recognizable collection of persistent state. It can be viewed as a page that contains info, memorable content, or links to other pages.
Screen: A general UI screen such as a pop-up window, dialog box, or splash screen that doesn’t contain memorable content. It isn’t a user-recognizable collection of persistent state.
The following figure illustrates a hypothetical app structure with an assortment of pages and screens.