Read original post at Timmy Kokke's Blog
A new control added in the Windows 8.1 preview is the Flyout control. It is used for temporarily showing some UI based on what the user is doing. It could be, or actually must be, easily dismissed by clicking or tapping outside it. You can attach the Flyout control to a button or use the FlyoutBase.AttachedFlyout attached property on any other framework element. Other than a dialog, the flyout does not create a window and does not block the UI.