I got a PM in my email but strangely not on this forum...weird... anyway the question was about NTFS junctions.

The NTFS node table is a logical structure that holds pointers to areas of the disk containing files and folders (ok the node table will actually contain the file if it is less than the cluster size). It is capable of having multiple pointers to the same logical disk structure. Mlink on Vista and Junction.exe on 2K/2K3 & XP allow you to create reparse points, additional pointers to the same directory or file (mlink only for file). Basically think of it as a shortcut but a low level one that applications treat as a real directory.

There is some better information on how to use them in the wiki Wiki - junction, Forum - NTFS Junction and Forum - mlink

hope this helps