This property returns reference to list of all virtual
folders defined globally. Virtual folders are non-existent
folders - but are visible to users that connect to your
server, and actually point to completely different location
on your file system.
VirtualFolders can be changed at run-time, and even when
users are connected.
When user connects to the server, this collection is
copied to User.VirtualFolders
collection - where you can change virtual folders 'per
user' basis.