The corners on your screen are called hot corners and give you access to different Windows features. The bottom Left-hand corner of the screen allows you to access the Start screen. If you're in the Start screen and have the Desktop open, this corner opens the Desktop from the Start screen. Right-clicking in the left hand corner opens the power user menu.
Moving the mouse to the top-left corner and then down displays all the apps running on the computer. Clicking and dragging any of these apps to the left or right-hand side of the screen will snap that app to that side of the screen. Each of these open app icons can also be right-clicked to close or snap. The full right-hand side of the screen will give you access to the Windows Charms.