Name Server Record. An NS record declares that a given zone is served by a given name server. Every NS record is either a delegation record or an authority Record. If the name of the NS record is the name of the zone it appears in, it is an authority record. If the name of the NS record is that of a descendant zone, then it is a delegation record.

BIND, a common Un*x DNS server, uses NS records in hint files for telling resolvers where to find root servers.