The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most prominently, it translates easily memorized domain name to the numerical IP addresses needs for the purpose of locating computer services and devices worldwide. By providing a worldwide, distributed keyword-based redirection service, the Domain Name System is an essential component of the functionality of the internet.

An often-used analogy to explain the Domain Name System is that it serves as the phone book for the internet by translating human-friendly computer hostnames into IP addresses. For example the domain name www.example.com translates to the addresses 192.163.0.10 (IPv4) and 2001:500:88:200::10 (IPv6). Unlike a phonebook the DNS can be quick updated, allowing a service's location on the network to change without effecting the end users, who continue to use the same hostname. Users take advantage of this when they use meaningful uniform resource locator (URL) and E-mail addresses without having to known how the computer actually locates the services.

The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name serves for each domain. Authoritative name servers are assigned to be responsible for their particular domain and in turn can assign other authoritative name servers for their sub-domains. This mechanism has made the DNS distributed and fault tolerant and has held avoid the need for a single central register to be continually consulted and updated. Additionally the responsibility for maintaining and updating the master record for the domain is spread among many domain name registers, who compete for the end-user's (the domain-owner's) business. Domain can be moved from one registrar to other registrar at any time.

The Domain Name System also specifies the technical functionality of this data base service. It defines the DNS protocol, a detailed specification of the data structures and data communication exchanges used in DNS, as part of the internet protocol suit.