This is one of the feature that I wished since the ages of XP.
and the feature is to add any folder to document folders without physically moving it to Document folder. let me explain, earlier to Windows 7 i a user have to add any folder like his songs folder to My Music folder of windows then he have to copy that song folder to My Music which is little problematic at least for me because first it takes to much time and second if because of some reason you have to format your windows you will lose all your document.
So thanks to guys at Microsoft they have come with a very smart solution that is to let you add a reference of song older in My Music rather than hole folder.
Let me show how it works.
you just have to select the folder you want to add to library and click the “Include in library” button this will show you option to where you want to add the folder chose according to content of folder and you are done now the folder will appear in your document folder as it is there.