Windows 8.1 fully integrates multitasking capabilities allowing you to seamlessly switch between your apps or use multiple apps simultaneously. As such applications downloaded from the Windows Store are automatically managed by your operating system (apps running in the background are automatically closed after a certain period of inactivity).
To close an app manually:
Method 1- Using a keyboard shortcut
Press Alt + F4 or Windows key + Down Arrow key to close app.
Method 2- Using the mouse cursor
Place the mouse cursor at the top of the app screen.
(1) A small (black) ribbon will be displayed, click on the close (x) button.
(2) Drag and drop the app window to lower edge of the screen, then release.
On touchscreen devices
Tap an hold on the application screen and drag the application icon to the bottom of the screen.