This term usually refers to a Domain Name System which translates textual names into their 32 bit Ip Addresses -- as in c2.com --> 209.162.215.78
Technically DNS stands for DomainNameSystem and a DNS server either answers queries or recursively queries other DNS servers until it gets an authoritative answer or the query times out.
A good resource for dns is http://www.dns.net/dnsrd/
- How does this system work?
Some are concerned with the Security Risks it presents.
The ManPage you want is the one for
dig @ns.example.net example.com