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 computer with Windows 7, a homegroup is created automatically if one doesn't already exist on your home network. If a homegroup already exists, you can join it. After you create or join a homegroup, you can select the libraries that you want to share. You can prevent specific files or folders from being shared, and you can share additional libraries later. You can help protect your homegroup with a password, which you can change at any time.
Using a homegroup is one of the easiest ways to share files and printers on a home network, but there are other ways to do this. For more information, see File sharing essentials
Computers must be running Windows 7 to participate in a homegroup. HomeGroup is available in all editions of Windows 7. In Windows 7 Starter and Windows 7 Home Basic, you can join a homegroup, but you can’t create one.