In Internet terminology, computers referred to as name servers provide services that maintain name- to-IP address mappings. These DNS name servers provide this information to client computers and programs that need to connect to other computers on a network.
When a user types a URL into an Internet browser, the browser first contacts a DNS name server to resolve the host and domain name portion of the URL to an IP address. After the DNS name server returns the name-to-IP address mapping, the browser can connect to the remote computer by using the IP address.
The Internet implementation of DNS distributes the responsibility for maintaining name-to-IP address mapping to DNS name servers located throughout the Internet. Each DNS name server on the Internet manages only a portion of the domain name space and is said to be authoritative for only that portion it manages. In other words, each DNS name server only maintains DNS data for the domain for which it is authoritative and no other.
When other name servers on the Internet need name-to-IP address mappings, they contact the authoritative name server for names of any computers contained within the domain for which the server is authoritative. This process allows the DNS data and management of that data to be distributed across the Internet.
A DNS name server can manage an entire domain or one or more subdomains by using administrative groupings referred to as zones. A zone is an administrative and DNS server database grouping used to manage all or part of an enterprise domain. If the domain is large (containing many subdomains and computers) the domain authoritative name server can delegate management of parts of the domain to one or more other DNS name servers.