When you open up Windows Explorer in Windows 7, you’ll notice the new “libraries” groups. Libraries are another way to group your data together and it can be much more useful than a drive letter or a Favorite. It’s a “super-folder” that shows you several folders at once.
Although each library is a collection of folders, it can be used in file operations such as save and open file dialog boxes. The library has a default “save location” that’s referenced when saving a file to library location. The save location is defined in the library properties.
At this point, network drives can only be included if the folder is available offline or indexed using Windows Search 4 or later. There are, however, workarounds others have published that describe how to get around this.