The Domain Name System (DNS) is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network.
DNS associates various information with domain names assigned to each of the participating entities. A Domain Name Service resolves queries for these names into IP addresses 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.
A good analogy to explain DNS 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 220.127.116.11 (IPv4) and 2620:0:2d0:200::10 (IPv6). Unlike a phone book, however, DNS can be quickly updated and these updates distributed, allowing a service’s location on the network to change without affecting the end users, who continue to use the same hostname. Users take advantage of this when they recite meaningful Uniform Resource Locators (URLs) and e-mail addresses without having to know 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 servers for each domain. Authoritative name servers are assigned to be responsible for their particular domains, 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 helped 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 domains is spread among many domain name registrars, who compete for the end-user’s, domain-owner’s, business. Domains can be moved from registrar to registrar at any time.