The domain namespace is divided into regions called zones. For instance, if you have example.com, you have the example section, or zone, of the com domain.
The DNS server is a server that maintains the name and IP information for a domain. You can have a primary DNS server for master zone, a secondary server for slave zone, or a slave server without any zones for caching.
Master zone DNS server
The master zone includes all hosts from your network and a DNS server master zone stores up-to-date records for all the hosts in your domain.
Slave zone DNS server
A slave zone is a copy of the master zone. The slave zone DNS server obtains its zone data with zone transfer operations from its master server. The slave zone DNS server responds authoritatively for the zone as long as it has valid (not expired) zone data. If the slave cannot obtain a new copy of the zone data, it stops responding for the zone.
Forwarders are DNS servers to which your DNS server should send queries it cannot answer.
The record is information about name and IP address. Supported records and their syntax are described in BIND documentation. Some special records are:
An NS record tells name servers which machines are in charge of a given domain zone.
The MX (mail exchange) records describe the machines to contact for directing mail across the Internet.
SOA (Start of Authority) record is the first record in a zone file. The SOA record is used when using DNS to synchronize data between multiple computers.