Source : Free On-Line Dictionary of Computing

whois
     
        An {Internet} directory service for looking up names of people
        on a remote server.  Many servers respond to {TCP} queries on
        {port} 43, in a manner roughly analogous to the {DDN} {NIC}
        whois service described in {RFC} 954.  Other sites provide
        this directory service via the {finger} {protocol} or accept
        queries by {electronic mail} for directory information.  On
        {Unix} the client command is
     
        	whois -h server_name person_name
     
        You can also type "telnet server_name 43" and then type the
        person's name on a separate line.  For a list of whois
        servers, FTP/Gopher: sipb.mit.edu.  Or
     
        	whois -h sipb.mit.edu whois-servers
     
        As the above command demonstrates, whois can find information
        about things other than users, e.g. domains, networks and
        hosts.
     
        See also {finger}, {X.500}, {white pages}.