Source : Free On-Line Dictionary of Computing

Value Added Network
     
         (VAN) A privately owned {network} that provides a
        specific service, such as legal research or access to a
        specialised database, for a fee.  A Value Added Network
        usually offers some service or information that is not readily
        available on public networks.
     
        A Value Added Network's customers typically purchase {leased
        lines} that connect them to the network or they use a {dial-up
        number}, given by the network owner, to gain access to the
        network.
     
        (1998-11-10)