A domain name (for instance, example.com) is an identification string that defines a realm of administrative autonomy, authority, or control on the Internet. Domain names are formed by the rules and procedures of the Domain Name System (DNS). Any name registered in the DNS is a domain name.
Domain names are used in various networking contexts and application-specific naming and addressing purposes. In general, a domain name represents an Internet Protocol (IP) resource, such as a personal computer used to access the Internet, a server computer hosting a web site, or the web site itself or any other service communicated via the Internet.
Domain names are organized in subordinate levels (subdomains) of the DNS root domain, which is nameless. The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, info, net, edu, and org, and the country code top-level domains (ccTLDs). Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are typically open for reservation by end-users who wish to connect local area networks to the Internet, create other publicly accessible Internet resources or run web sites. The registration of these domain names is usually administered by domain name registrars who sell their services to the public.
A fully qualified domain name (FQDN) is a domain name that is completely specified in the hierarchy of the DNS, having no omitted parts.
Domain names are usually written in lowercase, although labels in the Domain Name System are case-insensitive.
The Internet Corporation for Assigned Names and Numbers (ICANN, /ˈaɪkn/ eye-kan) is a nonprofit private organization headquartered in the Playa Vista section of Los Angeles, California, United States, that was created on September 18, 1998, and incorporated on September 30, 1998 to oversee a number of Internet-related tasks previously performed directly on behalf of the U.S. government by other organizations, notably the Internet Assigned Numbers Authority (IANA), which ICANN now operates.
ICANN is responsible for the coordination of the global Internets systems of unique identifiers and, in particular, ensuring its stable and secure operation. This work includes coordination of the Internet Protocol address spaces (IPv4 and IPv6) and assignment of address blocks to regional Internet registries, for maintaining registries of Internet protocol identifiers, and for the management of the top-level domain name space (DNS root zone), which includes the operation of root name servers. Most visibly, much of its work has concerned the DNS policy development for internationalization of the DNS system and introduction of new generic top-level domains (TLDs). ICANN performs the actual technical maintenance work of the central Internet address pools and DNS root registries pursuant to the IANA function contract.
ICANNs primary principles of operation have been described as helping preserve the operational stability of the Internet to promote competition to achieve broad representation of the global Internet community and to develop policies appropriate to its mission through bottom-up, consensus-based processes.
On September 29, 2006, ICANN signed a new agreement with the United States Department of Commerce (DOC) that moves the private organization towards full management of the Internets system of centrally coordinated identifiers through the Multistakeholder Model of consultation that ICANN represents.