# What Is a Domain Name? Structure, Registration, and DNS Lookup

> A domain name is the human-readable address that maps to a numeric IP address. Here is how the hierarchy, TLDs, registration, and DNS lookups work.

Source: https://camnangai.com/en/engineering/what-is-a-domain-name  
Published: 2026-07-27

A **domain name** is a unique, human-readable address for a resource on the internet.

It works as an easy-to-remember alias for complex numerical or alphanumeric IP addresses, letting you reach web
servers through a browser without memorizing the underlying routing coordinates.

When you enter a name into a browser, the Domain Name System (DNS) resolves that string into a
machine-readable address, and traffic is routed to the intended destination server. The domain name is
the entry point into a global, distributed database that maps names to network locations.


  That indirection is the whole point: services can move between physical servers or change their IP
  addresses entirely, and the address you type stays the same.


![A domain name as a memorable text address standing in for a server's numeric IP address](https://camnangai.com/articles/ten-mien-la-gi/01-infographic-en.webp)

## What is a domain name?

A **domain name** is a string of text that maps to an IP address, acting as the gateway for users to
reach websites through a browser. Computers identify each other using
[Internet Protocol (IP) addresses](https://camnangai.com/en/engineering/how-does-the-internet-work) — numeric dotted-decimal
IPv4 addresses such as `192.0.2.172`, or longer hexadecimal IPv6 addresses. Those strings are efficient
for machines and impractical for people.

The usual analogy is a phone's contact list. A smartphone stores complex phone numbers under a
searchable name, and DNS does the same job for the internet: you type human-friendly words into a
browser, and the system resolves them into the numerical address needed to reach a particular web
server.

Every website consists of two things — a domain name and a web server. The domain name is the street
address that points a browser at the files, code, and content sitting on that server. Because the
address is independent of the server behind it, you can replace the hardware without anyone noticing.

## The parts of a domain name: reading right to left

Domain names are structured hierarchically and read from right to left, moving from general identifiers
to specific labels. The hierarchy actually begins at the **root level**, represented by an invisible dot
at the end of every domain — `google.com.` is the fully qualified form. Each part of the domain,
separated by a dot, describes its position within that hierarchy.

![Domain name structure read right to left: top-level domain, second-level domain, and subdomain](https://camnangai.com/articles/ten-mien-la-gi/02-en.webp)

The section to the left of the root is the top-level domain (TLD), such as `.com` or `.org`. The label
immediately to the left of the TLD is the second-level domain (2LD), typically the unique name chosen by
the registrant. In `google.com`, `.com` is the TLD and `google` is the 2LD. More layered structures work
the same way: in `google.co.uk`, `.uk` is the TLD, `.co` is the 2LD indicating a commercial entity, and
`google` becomes the third-level domain (3LD). Similarly, `developer.mozilla.org` uses `developer` as a
subdomain to organize a distinct body of content.

Each label must follow formatting rules defined by core internet standards:

- **Length:** each label can be between 1 and 63 characters.
- **Characters:** only letters (A–Z), digits (0–9), and hyphens are permitted.
- **Hyphens:** a hyphen may not sit at the beginning or end of a label.
- **Case:** domain names are case-insensitive.

## Types of top-level domain (TLD)

TLDs are categorized by intended use, geographic association, or eligibility requirements. Generic TLDs
(gTLDs) are the most common and include traditional extensions like `.com` for commercial use, plus
`.net` and `.org`. Many newer gTLDs have since been introduced for niche branding, among them
`.app`, `.blog`, `.shop`, `.tech`, `.dev`, and `.io`.

![Categories of top-level domain: gTLDs, newer gTLDs, country-code TLDs, and restricted TLDs](https://camnangai.com/articles/ten-mien-la-gi/03-en.webp)

Country-code TLDs (ccTLDs) consist of two letters based on international country codes, indicating where
a site is registered or operates: `.uk` (United Kingdom), `.jp` (Japan), `.au` (Australia). Restricted
TLDs enforce stricter eligibility criteria — `.gov` is reserved for government departments, and `.edu`
is limited to educational and academic institutions.

Internationalized domain names (IDNs) allow non-Latin characters such as Arabic, Chinese, or Cyrillic
scripts. Because DNS is bound to the **ASCII character set**, IDNs use Punycode encoding to translate
non-ASCII characters into a standardized form beginning with `xn--`, which the existing global
infrastructure can process without modification.

## Domain name, URL, website, hosting: what is the difference?

These four terms get used interchangeably, and they describe different things. A URL (uniform
resource locator) is the complete address used to find a specific resource online. In
`https://cloudflare.com/learning/`, `https` is the protocol, `cloudflare.com` is the domain name, and
`/learning/` is the path to a specific page.

The rest is easiest to separate through a real estate analogy. Web hosting is the land — the server
space where website files are stored. That publicly reachable computer supplies the resources that keep
a site available. The website itself is the house: the collection of code, files, and images a visitor
actually interacts with.

![Domain name, URL, website, and hosting compared through the address, land, and house analogy](https://camnangai.com/articles/ten-mien-la-gi/04-en.webp)

The **domain name** is the street address for that house. It is the identifier people use to find the
location. A functional website needs both a place to host it and an address to reach it; neither one
alone gets a visitor to your content.

## Who manages domain names?

ICANN, the Internet Corporation for Assigned Names and Numbers, oversees the administrative hierarchy
and manages the global namespace. ICANN delegates management to domain registries — the
owners of TLDs such as `.com` — which in turn authorize registrars like GoDaddy or Cloudflare to lease
names to the public. Over 300 million domain names are registered today.

![The tiered domain governance chain: ICANN, registry, registrar, and registrant](https://camnangai.com/articles/ten-mien-la-gi/05-en.webp)

The system evolved out of the early internet, where developers manually mapped hostnames in a text file
called `HOSTS.TXT`. As the network grew, that approach stopped scaling. Paul Mockapetris invented DNS in
1983 to replace it, and responsibility initially sat with the Internet Assigned Numbers Authority (IANA)
before transitioning to ICANN in 1998.

Registration data lives in the WHOIS database, a public record you can query through a registrar's
search tool or the command-line `whois` utility. Querying a registered name like `mozilla.org` returns
its registrant — the Mozilla Foundation — along with creation date and domain status. Querying an
unregistered name such as `afunkydomainname.org` returns `NOT FOUND`, which is how you confirm a name is
free. Registrars require a valid real-world address at registration, and many offer WHOIS privacy
services to keep a registrant's personal contact details out of public view.

## Registering a domain name: you are leasing, not buying

Registering a domain name is a lease, not a permanent purchase. You pay for the right to use a specific
name for a period that typically runs 1 to 10 years. The current registrant holds priority for renewal,
but the name returns to the market if the fees stop.

![A domain name's lifecycle: registration, renewal, expiry, redemption period, and auction](https://camnangai.com/articles/ten-mien-la-gi/06-en.webp)

The expiration lifecycle includes a renewal window followed by a possible auction. A domain that is not
renewed can also fall to domain squatting, where a third party registers the name in bad faith to resell
it at an inflated price or to use it for phishing. To limit abuse, domains are subject to a 60-day
transfer lock after initial registration, and moving a domain between registrars requires an
authorization code from the current registrar.

Pricing runs from a few dollars a year to thousands, driven by market demand and by each registrar's
business practices. Premium domains cost more because they are short or map closely to a specific
industry. Choosing a trustworthy registrar matters more than the sticker price: some buy their own
customers' expired domains the moment they lapse, then sell them back at a steep markup.

## From a domain name to a website: how a DNS lookup works

A DNS lookup resolves a human-readable domain name into an IP address. When you type an address, the
browser first checks its local cache. If nothing is found, the query goes to a recursive resolver,
usually one provided by your ISP. That resolver then works down the hierarchy: root name server → TLD
name server → authoritative name server.

![The six steps of a DNS lookup from browser cache to the authoritative name server](https://camnangai.com/articles/ten-mien-la-gi/07-en.webp)

The authoritative server holds the definitive answer and returns the final IP address. That answer
travels back to the browser, which then connects to the host server. Caching and
**time-to-live (TTL)** values keep this efficient; TTL sets how long a server may hold a record before
it must be refreshed.

Because these records are distributed across servers worldwide, changes made at a registrar — such as
pointing a domain at a new host — are subject to **propagation delay**. Servers have to wait for the old
record's TTL to expire before they fetch updated data from the authoritative source, and that can take
several hours. Nothing is broken during that window; the old records have not aged out yet.

## How to choose a domain name

Picking a domain name is worth some thought, because it is often the first thing a customer judges
you on. Keep it short and memorable, and avoid numbers, hyphens, and uncommon spellings that are easy to
mistype. Relevant industry keywords help, as does a geographic marker if the business serves a specific
area.

Beyond the primary address, registering additional extensions such as `.net` or `.org` protects a brand
from competitors and squatters. A domain of your own also gives you a matching email address —
`info@yourbusiness.com` rather than a free mailbox — and that detail carries real weight with customers
deciding whether a business is serious.

## What should you learn next?

A domain name is only the addressing layer. To understand what runs underneath it — how packets travel,
what routers and ISPs actually do, and why IP addresses exist in the first place — read
[how the internet works](https://camnangai.com/en/engineering/how-does-the-internet-work) next.

From there, two natural directions are HTTP, the protocol a browser and server use to talk once the IP
address is known, and hosting, where a website's files physically live.

## References

- [What is a Domain Name? — MDN Web Docs](https://developer.mozilla.org/en-US/docs/Learn_web_development/Howto/Web_mechanics/What_is_a_domain_name)
- [What is a domain name? Domain names vs. URLs — Cloudflare Learning Center](https://www.cloudflare.com/en-gb/learning/dns/glossary/what-is-a-domain-name/)
- [Domain basics: What is a domain name? — Hostinger Academy](https://www.youtube.com/watch?v=lMHzpBwPuG8)
- [What is a domain name and do I need one? — GoDaddy](https://www.godaddy.com/resources/au/general-au/what-is-a-domain-name-and-do-i-need-one)
- [What Is DNS (Domain Name System)? — IBM](https://www.ibm.com/think/topics/dns)