What is a domain name? Plain-English guide

The short version

A domain name, like yourname.com.au, is a readable label. The DNS turns it into the numeric addresses computers use.
It reads right to left: the ending first (.au), then the name you chose, then anything you add in front.
You register the name. Subdomains in front of it, like shop.yourname.com.au, are yours to create.
You don’t own a domain name. You hold the right to use it for a set period, and you keep it by renewing.

A name for a number

Every server on the internet is reached by a numeric IP address, something like 203.0.113.10. Numbers are fine for computers and hopeless for people, so the internet keeps a giant lookup system, the Domain Name System (DNS), that turns names into numbers.

A domain name is your entry in that system. auDA, which administers Australia’s .au domain, describes a domain name as “a human-readable internet address that allows internet users to find websites and send emails without having to remember complex Internet Protocol (IP) addresses”.

The useful part is the separation. Your name stays the same while the numbers behind it change. Move your website to a new host and you update one record; every link, business card and email address keeps working.

The parts of a domain name

Take shop.yourname.com.au. The dots split it into parts, and the parts are read from right to left, from the most general to the most specific.

shop Subdomain Optional. You create it yourself, in your DNS.

yourname Your name The part you choose and register.

.com.au Extension .au is the top-level domain; com.au is a namespace inside it.

Read it right to left: Australia (.au), commercial (com), your name, then a subdomain of your choosing.

The top-level domain (TLD)

The last part of the name is the top-level domain. The DNS terminology standard, RFC 9499, defines it as “a zone that is one layer below the root, such as ‘com’ or ‘jp’”. TLDs come in two main kinds:

Generic TLDs (gTLDs) such as .com, .net, .org, .dev and .xyz. Most are open to anyone, anywhere.
Country-code TLDs (ccTLDs), two letters for a country or territory: .au for Australia, .nz for New Zealand, .uk for the United Kingdom. Each sets its own rules about who can register.

IANA’s Root Zone Database lists every TLD and who runs it.

The second level, and why .au has two endings

In yourname.com, your name sits directly under the TLD. Australia added a layer: for most of .au’s history, names were registered inside a namespace such as com.au (commercial), net.au, org.au (not-for-profits) or id.au (individuals). These namespaces aren’t for sale. The .au registry runs them alongside .au itself.

You can also register directly under .au, as in yourname.au. Either way, the part you register is the first label to the left of the ending. Our .com.au and .au direct pages cover who can register each.

Subdomains

Anything to the left of your registered name is a subdomain: www, shop, mail, staging. Nobody sells you these. Once you hold yourname.com.au, you create subdomains by adding DNS records, as many as you like, and each can point somewhere different.

Even www is just a subdomain that became a habit. www.yourname.com.au and yourname.com.au are two different names, and each needs its own record if you want both to work. www, redirects and forwarding covers how to tie them together.

The whole thing is a tree

Put every domain name together and you get an upside-down tree. The root is at the top, TLDs hang off it, and every name hangs off the one above. Reading a domain right to left is walking down the tree.

Each level hands responsibility to the one below it. That hand-off is called delegation, and lesson 5 is all about it.

What makes a valid name?

The rules come from the original DNS specification, RFC 1034:

Letters, digits and hyphens only. No spaces, underscores or punctuation, and a hyphen can’t be the first or last character of a part.
Up to 63 characters per part. Each label between the dots “must be 63 characters or less”, and the full name is capped at 255 bytes, a limit you’ll never hit.
Capitals don’t matter. Names are compared “in a case-insensitive manner”, so YourName.com.au and yourname.com.au are the same name.

Individual registries add their own rules on top, such as who is eligible and which names are reserved.

A domain name isn’t a website (or an email account)

These get mixed up constantly, so it’s worth pulling them apart:

Thing	What it is	Example
Domain name	The name itself. It can exist with nothing attached to it.	`yourname.com.au`
Website	Files on a web server. The domain points at that server.	Your pages, hosted somewhere
Web address (URL)	The full address of one page: how to connect, which name, which page.	`https://www.yourname.com.au/menu`
Email address	A mailbox at a mail provider. The domain tells senders which provider.	`hello@yourname.com.au`

The website and the mailboxes are separate services, often from separate companies. They hang off the domain through DNS records, which is why you can swap web hosts or email providers without changing your name.

You hold a licence. You don’t own it.

People say they “bought” a domain, but nothing is sold outright. For .au names, auDA puts it plainly: “When you register a domain name you don’t ‘own’ it, instead you’re granted permission to use the domain name for specific period of time via a licence.”

Other extensions use different wording, but the deal is the same everywhere: you register the name for a set period, and you keep it for as long as you keep renewing. Let it lapse and, after a grace period, anyone eligible can register it. Renewal and expiry has the timeline.

What registration actually gets you. One line in the registry’s database: this name, held by this person or business, answered by these nameservers. That last part is the powerful bit. It decides where the whole internet goes looking for your website and email, and it’s the subject of Nameservers and DNS zones.

Terms in this lesson

Domain name: A readable name, such as yourname.com.au, that stands in for the numeric addresses computers use.
TLD: The last part of a domain name: .au, .com, .org.
ccTLD: A two-letter ending for a country or territory, such as .au, .nz or .uk.
gTLD: An ending that isn’t tied to a country, such as .com, .net, .org, .dev or .xyz.
Second-level domain: The part directly to the left of the top-level domain.
Subdomain: Anything in front of your registered name, such as shop.yourname.com.au.
www: Just a subdomain that became a habit.
URL: The full address of one page: how to connect, which name and which page, as in https://www.yourname.com.au/menu.
Licence: What you actually hold when you register a .au domain: the right to use the name for a set period.

Every term, in full, is in the glossary.

Sources

All read on 2 October 2026.

RFC 1034, Domain Names: Concepts and Facilities (IETF): label and name length limits, allowed characters and case-insensitive comparison.
RFC 9499, DNS Terminology (IETF): the definition of a top-level domain.
Root Zone Database (IANA): the list of every top-level domain and its manager.
Glossary of domain name terms (auDA): the definitions of a domain name and a domain name licence.
The .au registry (auDA): the registry runs the nameservers for .au and for second-level namespaces such as com.au.

A name for a number

The parts of a domain name

The top-level domain (TLD)

The second level, and why .au has two endings

Subdomains

The whole thing is a tree

What makes a valid name?

A domain name isn’t a website (or an email account)

You hold a licence. You don’t own it.

Terms in this lesson

Sources

Bring your domains over, or start a new one.