There's nothing more controversial in Windows 8 than Microsoft's decision to remove the Start button from the desktop in this release. But give the company a bit of credit: The Start menu that sat behind the Start button had been replaced by the new, full-screen Start screen and in the interests of consistency, Microsoft instead came up with a new interface that those used to the Start button should have little trouble using. It's called the Start tip.
The Start tip is unique in that it's a mouse-only feature that works with one of Windows 8's new hot corners, so called because each corner of the PC's main screen engages a new interface. With a keyboard, you can simply tap the Windows key to achieve the same effect. And those with Windows-based devices can use the Windows key button.
To see the Start tip, move the mouse cursor into the lower left corner of the screen (or, on a multi-monitor set up, the main screen). As you do, you'll see a small thumbnail appear. If you're currently viewing the desktop or a Metro-style app, this thumbnail, called the Start tip, will resemble a miniature version of the Start screen, providing a visual indication of its use.
To use it, simply click.
If you're already on the Start screen, the Start tip will feature a thumbnail of the previously-accessed interface, which is typically a Metro-styled app, including PC Settings, or the Windows desktop.
In this way, the Start tip mimics the use of the Windows key (or Windows key button). That is, it's a toggle that doesn't always cause you to navigate to the Start screen. Instead, it will toggle the display between the current view and the Start screen.
Note: Don't forget that you can right-click on the Start tip to access the new power-user menu as well. Keyboard users can access that menu by typing WINKEY + X.