The Domain Name System (DNS) is a distributed database system that provides hostname-to-IP resource mapping (usually the IP address) and other information for computers on an internetwork. Any computer on the Internet can use a DNS server to locate any other computer on the Internet.
DNS is made up of two distinct components:
The DNS hierarchy specifies the structure, naming conventions, and delegation of authority in the DNS service.
The DNS name service provides the actual name-to-address mapping mechanism.