"Peek gives you the power of X-ray vision, so you can peer past all your open windows straight to the Windows 7 desktop. Simply point to the right edge of the taskbar—and watch open windows instantly turn transparent, revealing all your hidden icons and gadgets.
So far so good, and here is where it gets 'useful'
To quickly reveal a buried window, point to its taskbar thumbnail. Now only that window shows on the desktop.
You can follow this tutorial in case you want to disable ""Aero Peek""
Off Topic: if you want to pep up Aero Peek a little bit, have a look at T3Desk, a slick, 3D window manager with Aero Peek support.
Hover a specific thumbnail, and Aero Peek kicks in to display the program's shrunken 3D view.
"My guess is that Aero Peek was added for consistency. If you are able to peek at a window by hovering on the window's thumbnail, you should be also able to do it with the desktop, which, after all, is a window by itself (it does show with the other windows when you press Win-Tab)
And, if you have gadgets, the Aero Peek is definitely useful, just as useful as when you hover on your Twitter app thumbnail to peek at your timeline."
