What is a domain?
A domain name is an identification
string that defines a realm of
administrative autonomy, authority
or control within the Internet.
Domain names are used in various
networking contexts and for application-specific
naming and addressing purposes.
In general, a domain name identifies
a network domain, or it 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.
In 2017, 330.6 million domain
names had been registered.[1]
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 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 with all
labels in the hierarchy of the
DNS, having no parts omitted.
Labels in the Domain Name System
are case-insensitive, and may
therefore be written in any desired
capitalization method, but most
commonly domain names are written
in lowercase in technical contexts.*
