When you set the Desktop to be the sidebar app using Windows 8's Snap feature, open applications appear as Peek windows. This lets you switch from the Windows 8 UI app taking up most of the screen to any Desktop application running in the sidebar.

In the example below, I have the Windows 8 UI version of Internet Explorer 10 open to Tom's Hardware as the sidebar app on the right. The Desktop is the main app open on the left, and you can see another instance of IE10, the Control Panel, and Microsoft's File Explorer.

Now, when I slide the separator towards the Desktop to make it the sidebar app, expanding the Window 8 UI version of IE10, the Desktop is represented by Peek windows of my three open apps.

If you have too many Desktop applications open to fit in the sidebar strip, then they start scrolling (unlike Windows 8 UI apps in the Switcher; remember those just disappear).

Beyond the Windows 8 UI-based version of Snap, the Desktop retains its own 50/50 Snap from Windows 7. And, believe it or not, both Snap features can be used together.

Provided that the Desktop is the main app, you can snap Desktop applications to both halves of the main screen. In the shot below, I have the Bing Weather app in the left-hand sidebar, while the Desktop takes up the rest of the space on the right. Within the Desktop, IE10 is snapped to the left, while File Explorer is snapped to the right, making the coveted triple-snap a reality!