See What Apps Are Running

If you launch a Windows 8 app, play with it for a while, then press the Windows key you'll switch back to the Start screen. Your app will remain running, but as there's no taskbar then you might be wondering how you'd ever find that out. You could just press Alt+Tab, which shows you what's running just as it always has. Holding down the Windows key and pressing Tab displays a pane on the left-hand side of the screen with your running apps. (To see this with the mouse, move your cursor to the top left corner of the screen, wait until the thumbnail of one app appears, then drag down.)