How to Use the Windows 8.1 Start Button
You gave instant access to the Start Screen.
If you left-click or tap the Windows 8.1 Start Button, you'll open the Start Screen and have access to all of your apps. Interestingly, if you have multiple monitors connected to your PC, clicking the Start Button opens the Start Screen on the monitor where you clicked. In other words, you can open the Start Screen on any monitor you want.
A left click on the Windows 8.1 Start Button functions exactly as if you press the Windows key on your keyboard. In both cases, the Start Screen opens on the currently active monitor.