In Windows Vista you had, Documents, Downloads, Photos, Videos, and Music. Whereas in Windows 7, Windows 8 and Windows 10 you see, Personal Documents, Personal Downloads, Personal Photos, Personal Videos, and Personal Music. You will also see a change in naming in the Public User Profile: Public Documents, Public Downloads, Public Photos, Public Videos, and Public Music. These folder structure changes were made to accommodate a new Windows Explorer feature in Windows 7 called Libraries.
Libraries can be accessed from the Navigation Pane of Windows 10/8/7 Explorer.
Libraries can be shared with other people on your Home network through a new network sharing feature in Windows called HomeGroup.
A HomeGroup makes it easier to share files and printers on a home network. You can share pictures, music, videos, documents, and printers with other people in your homegroup. Other people can’t change the files that you share, unless you give them permission to do so.
When you set up a homegroup, you select the libraries and devices that you want to share. You can prevent specific files or folders from being shared, and you can share additional libraries and devices later. You can help protect your homegroup with a password, which you can change at any time.
UPDATE: HomeGroup has been removed from Windows 10 version 1803.
How to Create your HomeGroup in Windows
Open Control Panel > HomeGroup > Create Now.
The HomeGroup wizard will prompt you to create your HomeGroup and choose what to share in it. It also then generates a password which can be used to add other connected computers to your HomeGroup. Once the HomeGroup is created, your Pictures, Music, Videos, Printers folders, called your Libraries, are ready to be shared with other computers when they join this HomeGroup.
How to Join a HomeGroup in Windows
When your other computer is connected to the same network where you have created the HomeGroup, Windows 7 will prompt you about a HomeGroup available to join. Click Join Now. Enter password. With this, you will have joined the HomeGroup and you will be able to choose what to share.
How to add an existing folder to the Library
Simply drag and drop it there.
How to create a New library
Open Libraries, right-click in the folder and select New Library.
Name it. Open it and click on Include a Folder to add your desired folders to this library.
If you don’t like or use this feature, you can always Disable Homegroup & Libraries in Windows.