Source : Free On-Line Dictionary of Computing

Uniform Naming Convention
     
         (UNC) Used in {IBM PC} networking to completely
        specify a directory on a {file server}.
     
        The basic format is:
     
        	\\servername\sharename
     
        where "servername" is the {hostname} of a network file server,
        and "sharename" is the name of a networked or shared
        directory.  Note this is not the same as the conventional
        {MS-DOS} "C:\windows" directory name.  E.g.
     
        	\\server1\dave
     
        might be set up to point to
     
        	C:\users\homedirs\dave
     
        on a server called "server1".
     
        It is possible to execute a program using this convention
        without having to specifically link a drive, by running:
     
        \\server\share\directory\program.exe
     
        The {undocumented} DOS command, TRUENAME can be used to find
        out the UNC name of a file or directory on a network drive.
     
        (1995-11-14)