Sign in with the account you use for SkyDrive, Xbox LIVE, Outlook.com, or other Microsoft services.
Sign in with the account provided by your work or school to use with Office 365 or other Microsoft services.
A shared folder is a special type of workspace that enables you to share the contents of a folder in your Windows file system across all computers on which you have your account, and with other users by invitation.
When you invite people to join a shared folder, they select a folder for sharing on their computers. All members of a shared folder have access to its contents (files and subfolders).