The Domain Name System (DNS) is the name service provided by the Internet for TCP/IP networks. It was developed so workstations on the network could be identified with common names instead of Internet addresses. DNS performs naming between hosts within your local administrative domain and across domain boundaries.
The collection of networked workstations that use DNS are referred to as the DNS namespace. The DNS namespace can be divided into a hierarchy of domains. A DNS domain is simply a group of workstations. Each domain is supported by two or more name servers (a principal server and one or more secondary servers). Each server implements DNS by running a daemon called named.
On the client side, DNS is implemented through a resolver. The resolver's function is to resolve user queries; to do that, it queries a name server, which then returns either the requested information or a referral to another server.