By default users are allowed to share files within their profile to other users on their network once an administrator opts ...

By default users are allowed to share files within their profile to other users on their network once an administrator opts in the computer.  An administrator can opt in the computer by using the sharing wizard to share a file within their profile.

If you enable this policy, users will not be able to share files within their profile using the sharing wizard.  Also, the sharing wizard will not create a share at %root%\users and can only be used to create SMB shares on folders.

If you disable or don't configure this policy, then users will be able to share files out of their user profile once an administrator has opted in the computer.