Introduction
Aero Peek is a new feature introduced with Windows 7. It is available with Windows 7 Home Premium Edition, Professional Edition and Ultimate Edition. With Aero Peek you can peek on your desktop or into thumbnail preview of an opened Window on your taskbar. What this feature does is to make all the active windows transparent and you will be able to see/peek your desktop/thumbnail window without minimizing all your currently opened windows.
Aero Peek is available when you are using Windows 7 Home Premium Edition, Professional Edition and Ultimate Edition, and are using an Aero theme.
Desktop Peek
The Aero Peek feature can be activated using a keyboard shortcut Windows Key 
 + Spacebar, you can also use it by pointing your mouse to the extreme right hand side of the taskbar over the Show desktop vertical button
To have a peek at the desktop, move the cursor to the extreme right corner of the task bar and keep the cursor on the small vertical button. This will make all the currently opened windows transparent and you will be able to see your desktop without closing any window. If you intend to work with you desktop and want to minimize all currently opened windows, then all what you have to do is to click on the Show desktop vertical button.
Check below snapshots :
Before Aero Peek :
Using Aero Peek :
Thumbnail Peek
Another feature of the Aero Peek is the ability to preview an opened file or Windows. Point your mouse pointer to the file/program/Window icon in the task bar and then hover over the thumbnail that pops ups. You will notice that everything else got transparent except the windows you are peeking into. This gives you the ability to look into this window without having to close other windows or minimizing them.
How To Disable/Enable Aero Peek :
To Disable the Aero Peek feature , right click on your taskbar then click Properties. Under the Preview desktop with Aero Peek section, you can deselect the Use Aero Peek to preview the desktop to disable Aero Peek
Summary
Windows 7 Aero Peek is a new features introduced with Windows 7. It offers two functions. First, it can be used to peek behind all of the opened windows. Second, it can be used to preview a thumbnail window on your taskbar
