Edu Azevedo asked me about Windows 7’s Libraries (they’re also in Windows 8), and why one should store files there.
To the uneducated eye, Windows’ libraries are simply convenient places to store your data files, such as documents, spreadsheets, pictures, music, and videos. And they are convenient. They make it easier to find, organize and back up the most important files on your hard drive.
But they’re not actually places—in the sense that they’re not folders on your hard drive. They’re pointers to other folders, and each library can point to more than one folder. For instance, the Documents library by default points to two different folders: My Documents and Public Documents. (The difference? Other people can more easily access the Public Documents.)
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Unhide libraries in Windows 8
Microsoft introduced libraries with Windows 7, then it hid them in Windows 8. If you use Windows 8, you can (and should) unhide them. In File Explorer, click the View tab, then the Navigation pane pull-down menu in the upper-left corner. Select Show libraries.
When you open Windows Explorer (Windows 7) or File Explorer (Windows 8— after making the change above), it automatically opens to the libraries. You can also find them in Windows/File Explorer’s Navigation pane, on the left side of the window.

Library view
The names Music, Pictures, and Videos are self-explanatory, but Documents can be a bit confusing. It’s not just for word-processing files. The Documents library is for any data files that don’t clearly belong in one of the other libraries. For instance, I prefer to keep all of the files associated with a particular project—including pictures—in a folder for that project within the Documents library.
Since a library merely points to existing folders, you can easily add other folders to it. This comes in handy, for instance, if you want to keep new documents on an SSD and older ones on a hard drive.
To do this, right-click a folder and select Include in library, and then select the appropriate library.
As a general rule, it’s always a good idea to separate code (Windows, the Registry, installed applications, and so on) from data (documents, photos, and other files you create and edit). Libraries make this happen pretty much automatically.