NS Records

NS records are zone file entries that delegate which servers are authoritative for a zone.

For example:

Origin                  TTL     Inet    Type    Entry 
sagonet.com.            300     IN      NS      ns2.sagonet.com.
sagonet.com.            300     IN      NS      ns1.sagonet.com.

So for sagonet.com, there are two name severs, ns1 and ns2. Thats it!

A fun way to look for a NS record is with the host command:

kyle@kyle-laptop:~$ host -t ns sagonet.com (the -t is for type)
sagonet.com name server ns2.sagonet.com.
sagonet.com name server ns1.sagonet.com.