Buying a domain name is often the first thing an entrepreneur does when considering a business idea. But what is a domain? How can it help build or protect your brand? And who’s who and who does the business of registering and managing domains?

This guide explains the jargon of the domains and should be read in conjunction with two other resources:

What is a domain name?

Each computer connected to the Internet has a unique numerical address called an IP address. These long numbers allow information like emails and requests for a particular web page to get to the right place. Long numbers are hard for people to remember so most of the time we use a user-friendly substitute for the IP address called a domain name. A domain name is just an easy to remember label for a very long number.

Domain names identify particular web pages and are also used in e-mail addresses. Domain names, like brands, are more memorable and distinctive than a number.

If you look in a browser address bar, you’ll see an address that contains a domain name and other information. The full address is known as a universal resource locator (URL). The URL directs your browser to exactly the place on the website you want to go.

Every domain name has three levels, as you can see from the table below.

3rd level domain or subdomain 2nd level domain or subdomain Top-level domain or extension
www. ThinkBusiness  .ie

Top-level domain

The ‘.ie’ part of the domain name is called the top-level domain or TLD. This is sometimes called an extension. Extensions like ‘.ie’ and ‘co.uk’ are known as country code top-level domains or ccTLDs. These are targeted at or connected with sovereign countries.

Extensions like ‘.com’, ‘.net’ and ‘.gov’ are generic top-level domains or gTLDs. These are associated with particular categories of websites such as business, internet service providers, travel firms and even government departments.

There are many new extensions being introduced all the time based on geographic, community, brand and other generic categories, such as .london, .irish, .apple and .plumber.

There are also internationalised domain names (IDNs) with a TLD that use Chinese, Arabic or some other form of non-Latin script. A list of all TLDs is available on the Internet Assigned Numbers Authority website.

Second level domain

This is called ‘the label’, and is often based on the name of a company or organisation (or a product or service).

Third level domain

For this domain, ‘www’ identifies the address as a set of web pages. The third level domain is almost always ‘www’ – however it might be ‘ftp’ (file transfer protocol), which denotes a site used for transferring files. It could also be a ‘subdomain’. For instance, we could set up a separate website that contained only the checklists from ThinkBusiness.ie and use a subdomain called ‘checklists.ThinkBusiness.ie’ to identify it.

The domain name system (DNS) is coordinated worldwide by a not-for-profit organisation called the Internet Corporation for Assigned Names and Numbers (ICANN). Each TLD has only one authoritative registry appointed by ICANN to maintain a register of domain names for each TLD. For example, national registries look after ccTLDs. The IE Domain Registry (IEDR) looks after domains with the ‘.ie’ extension.

Registrars are companies accredited by ICANN or a national registry like the IEDR to process applications for a domain name, if it is available. The registrar does this through the registry, which maintains the authoritative database for the domain that you have selected.