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Domain Name Glossary: Plain-English Definitions

Updated October 2026

The words used around domain names, explained simply.

Terms A to Z

Appraisal

An estimate of a domain's value. Automated appraisals such as TLD.is are second opinions, not offers.

Comparable sales ("comps")

Completed sales of similar names, used as evidence of what a domain might be worth.

Country-code top-level domain (ccTLD)

A two-letter domain ending assigned to a country or territory, such as .fr or .nz.

DNS

The domain name system, which translates names like example.com into the addresses computers use.

Domain hack

A name that uses the extension as part of a word, such as stud.io.

Expired domain

A domain the holder did not renew. After a grace period it may be released for anyone to register.

Generic top-level domain (gTLD)

A domain ending not tied to a country, such as .com, .org or .app.

hreflang

An HTML tag that tells search engines which language or country version of a page to show.

IANA

The Internet Assigned Numbers Authority, which maintains the root zone list of all TLDs.

ICANN

The non-profit organisation that coordinates the domain name system, including the contracts for gTLDs.

Internationalised domain name (IDN)

A domain using non-Latin characters, including country codes such as .рф (Russia) or .中国 (China).

ISO 3166-1

The international standard of two-letter country codes that most ccTLDs follow.

Liquidity

How quickly and easily a domain can be sold for a fair price.

Local presence requirement

A rule that registrants must have a real connection to the country, such as residence or a registered business.

Nameserver

A server that answers DNS questions for a domain. Changing nameservers moves a domain to a different DNS provider.

Premium domain

A name the registry or registrar prices above the standard rate, sometimes with higher renewals too.

Registrant

The person or organisation that holds a domain name.

Registrar

A company that sells domain names to the public and registers them with the registry.

Registry

The organisation that runs a TLD and sets its rules, such as DENIC for .de or Nominet for .uk.

Renewal

The yearly (or multi-year) fee to keep a domain. It can differ from the first-year price.

Root zone

The top of the DNS hierarchy, which lists every TLD and where to find it.

Second-level domain

The part directly to the left of the TLD: "example" in example.com. Some countries also use second-level endings such as .co.uk.

Top-level domain (TLD)

The last part of a domain name, after the final dot.

Trustee service

A service where a local party registers a restricted ccTLD on your behalf. The trustee may be the legal registrant.

UDRP

The Uniform Domain-Name Dispute-Resolution Policy, used for trademark disputes on gTLDs and some ccTLDs.

WHOIS / RDAP

Lookup systems that show registration details for a domain, subject to privacy rules.

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