What is a domain name? (and how it maps to an IP address)

The one-sentence definition

A domain name is a human-friendly name that stands in for an IP address. Computers route traffic using numbers — an address like 93.184.216.34 for IPv4, or something longer for IPv6 — but numbers are hard to remember, they change when you move servers, and they leak nothing about what a site actually is. A domain name such as example.com solves all three problems at once: it is easy to remember, it can point at a different IP tomorrow without anyone noticing, and it can carry a brand. The name is not the destination. It is a stable label that the network looks up to find the destination.

If you have ever wondered what number your own name currently points at, the IPFerret home page shows the public IP you are connecting from right now — the numeric side of this whole story.

Anatomy of a domain — read it right to left

The counter-intuitive rule is that domain names are read from right to left, from the most general part to the most specific. Take www.blog.example.com and walk it backwards:

The root — the dot you never type

At the very right there is an implied trailing dot: the fully-written form is www.blog.example.com. That final dot is the root of the entire domain name system — the silent, unnamed top of the hierarchy. You almost never type it, but every name technically ends there, and every lookup starts there.

The top-level domain (TLD)

Just left of the root sits the top-level domain: the com in example.com. TLDs come in a few flavours. There are the classic generic TLDs — .com, .org, .net — that anyone can generally register. There are country-code TLDs (ccTLDs) tied to a territory: .uk, .de, .jp, .io. And there is a large crop of newer generic TLDs introduced from 2013 onward — .app, .dev, .shop, .xyz and hundreds more. Each TLD is run by a designated registry that keeps the master list of names under it.

The registrable domain (second level)

Left of the TLD is the label you actually register: example in example.com. The combination of that label plus the TLD — example.com — is the registrable domain, sometimes called the second-level domain or the apex. This is the unit you pay for and control. Once it is yours, everything to the left of it is yours to arrange however you like.

Subdomains

Everything further left is a subdomain that you create under your registrable domain, for free, as many as you want. In www.blog.example.com, both blog and www are subdomains. www is a convention, not a requirement — it is just a subdomain that historically pointed at a web server, which is why example.com and www.example.com can behave differently unless you deliberately point them at the same place. mail.example.com for a mail server is another common example.

Domain vs URL vs hostname vs FQDN

These four terms get used interchangeably and they should not be. Here is the clean version.

• Domain name — the registrable name itself, e.g. example.com. No scheme, no path.
• Hostname — a name that identifies a specific host (machine or service), e.g. www.example.com or mail.example.com. A hostname is a domain name with a host label on the front.
• FQDN — a Fully Qualified Domain Name is a hostname written out completely to the root, with the trailing dot: www.example.com. It is unambiguous — there is no context left to fill in — which is why DNS internally works with FQDNs.
• URL — a Uniform Resource Locator is the full address of a specific resource. It wraps a domain in everything needed to fetch something: a scheme, an optional host, a path, and sometimes a query string. In https://www.example.com/pricing?ref=home, the scheme is https, the host is www.example.com, the registrable domain is example.com, and /pricing is the path.

The short version: a domain is the name, a hostname points at a machine, an FQDN is the fully-spelled hostname, and a URL is the whole address bar. Every URL contains a domain (or a bare IP address), but a domain by itself is not a URL.

How a name becomes an IP — DNS resolution

When you type a name, nothing can happen until it is turned into an IP address. That translation is the job of the Domain Name System, and it mirrors the right-to-left structure of the name itself. In rough order:

1. Ask the root. A resolver starts at the root and asks: who handles .com? The root servers reply with the location of the .com TLD servers.
2. Ask the TLD. The resolver asks the .com servers: who is authoritative for example.com? They reply with the domain's nameservers.
3. Ask the authoritative nameservers. Finally the resolver asks those nameservers for the exact record it needs — usually the A record (IPv4) or AAAA record (IPv6) — and gets back the IP address to connect to.

Answers are cached along the way so this full walk does not happen on every request. The mechanics — recursion, caching, TTLs, and why the whole thing is fast despite the number of hops — are covered in how DNS works. The individual record types you will meet along the way are explained in DNS record types, and there is a broader overview of the system at the DNS explainer.

Who runs it all

The naming system is not owned by any one company. It is a layered arrangement of responsibilities, and it helps to know who does what.

• ICANN — the Internet Corporation for Assigned Names and Numbers is the non-profit that coordinates the whole system: it decides which TLDs exist, accredits registrars, and sets the policies the rest of the chain follows. It does not sell you a domain directly.
• Registries — each TLD has one registry operator that runs the authoritative database of every name under that TLD and the nameservers for it. The registry for .com keeps the master list of all .com names.
• Registrars — the accredited companies you actually buy from (and their resellers). They take your order, record you as the owner in the registry, and handle renewals and settings on your behalf.
• You, the registrant — the person or organisation the name is registered to. You hold the rights to use it for as long as the registration is active.

When people say they “bought a domain,” what actually happened is more modest: you did not buy anything outright. You lease the exclusive right to use that name for a fixed term — commonly one to ten years — and you renew to keep it. The registry still owns the underlying entry; you are recorded as the registrant. Let the lease lapse and the name goes back into the pool.

Nameservers and pointing a domain

Registering a name and making it do something are two separate steps. A fresh domain has no destination until you tell it where to point. That happens through nameservers: at your registrar you set which nameservers are authoritative for your domain, and those nameservers hold the actual records.

The two records you will reach for most often are the A record, which maps a name straight to an IPv4 address, and the CNAME record, which points one name at another name (handy when you want www.example.com to follow wherever example.com or a hosting provider's hostname goes). Point the apex with an A record to your server's IP, add a CNAME for www, and the name resolves. The full catalogue — including MX for mail, TXT for verification, and AAAA for IPv6 — lives in DNS record types.

WHOIS and registration data

Every registration leaves a record. WHOIS (and its successor protocol RDAP) is the public directory that exposes registration data for a domain or an IP address: when it was created, when it expires, which registrar holds it, and — depending on privacy settings and jurisdiction — contact details. Much of the personal contact information is now redacted behind privacy services or masked to comply with data-protection rules, but the administrative facts (registrar, dates, status) remain visible.

You can inspect this kind of registration data with IPFerret's WHOIS lookup, and if you are curious how long a name has been around, the domain age tool reads the creation date from the same registration record.

Domain expiry

Because a domain is a lease, it has an expiry date, and letting it slip has real consequences. When a registration lapses it does not vanish instantly. It usually moves through a grace period during which you can still renew at the normal price, then a redemption period where recovery costs a hefty fee, and finally a pending-delete window after which the name drops and anyone can register it again. Sought-after names are snapped up within seconds of dropping. The practical advice is dull but important: keep auto-renew on, keep the billing card current, and keep the registrant email address one you actually read — expiry notices go there.

Frequently asked questions

What is the difference between a domain name and a URL?

A domain name is just the name part — example.com. A URL is the full address of a specific resource and contains the domain plus more: a scheme (https://), an optional subdomain and host, an optional path (/pricing), and sometimes a query string. So https://www.example.com/pricing is a URL; example.com is the registrable domain inside it. Every URL contains a domain (or a bare IP), but a domain on its own is not a URL.

Do you actually own a domain name when you register it?

No — you lease the right to use it for a fixed term, typically one to ten years, and you renew to keep it. The registry that runs the TLD owns the underlying database entry; your registrar records you as the registrant and holds the registration on your behalf. If you stop paying, the name expires and eventually returns to the available pool for someone else to register.

How does a domain name become an IP address?

Through DNS resolution. A resolver reads the name right-to-left: it asks a root server which servers handle the TLD (like .com), asks those TLD servers which authoritative nameservers hold the domain's records, then asks those nameservers for the specific record — usually an A record (IPv4) or AAAA record (IPv6). The returned IP is what your device actually connects to; the name was only ever a lookup key.

Related reading

• How DNS works — the resolution walk from root to authoritative nameserver, in detail.
• DNS record types — A, AAAA, CNAME, MX, TXT and the rest, and what each one points at.
• The DNS explainer — the broader picture of how the name system fits together.
• WHOIS lookup — read the registration record behind a domain or IP.
• Domain age — how old a name is, straight from its creation date.
• The glossary — quick definitions for the networking terms in this article.