App Bar in Windows Store App
What are App Bars in Windows Store App
Outside of the app page, the app bar is the primary command interface for your app. Use the app bar to present navigation, commands, and tools to users. The app bar is hidden by default and appears when users swipe a finger from the top or bottom edge of the screen. It covers the content of the app and can be dismissed by the user with an edge swipe, or by interacting with the app.
A Windows Store app can have a top or a bottom app bar.