I have been always fascinated by these shell folders like my documents, my pictures and my music etc as they can reside some where on your desktop and start menu which makes them easy to access and they can not be deleted or renamed.
All these shell folders in windows are based on folder redirection principle where a particular folder space is being redirected to a specific path in windows like My Pictures or My Documents will be actually placed in Documents and Settings >> Username >> My Documents or My Pictures
My Shell Folder allows you to create shell folders like My Documents, My Pictures which will be shown in My Computer and stay on your desktop and they cannot be deleted or renamed.