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. It associates various information with domain names assigned to each of the participating entities. Most importantly, it translates domain names meaningful to humans into the numerical identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide.
An often-used analogy[by whom?] to explain the Domain Name System is that it serves as a phone book for the Internet by allowing the looking-up of human-friendly computer hostnames where we find (or have found) the associated IP addresses in much the same way we look up a name in a phone-book to find the associated phone-number. With DNS we type the domain name into our browser address bar and the DNS looks up the associated numerical identifier or IP address. For example, the domain name www.example.com translates to the addresses 126.96.36.199 (IPv4) and 2620:0:2d0:200::10 (IPv6).
The Domain Name System makes it possible to assign domain names to groups of Internet resources and users in a meaningful way, independent of each entity's physical location. Because of this, World Wide Web (WWW) hyperlinks and Internet contact information can remain consistent and constant even if the current Internet routing arrangements change or the participant uses a mobile device. Internet domain names are easier to remember than IP addresses such as 188.8.131.52 (IPv4) or 2001:db8:1f70::999:de8:7648:6e8 (IPv6). 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 them.
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.
In general, the Domain Name System also stores other types of information, such as the list of mail servers that accept email for a given Internet domain. By providing a worldwide, distributed keyword-based redirection service, the Domain Name System is an essential component of the functionality of the Internet.
Other identifiers such as RFID tags, UPCs, International characters in email addresses and host names, and a variety of other identifiers could all potentially use DNS.
The Domain Name System also specifies the technical functionality of this database service. It defines the DNS protocol, a detailed specification of the data structures and communication exchanges used in DNS, as part of the Internet Protocol Suite.