Domain names can be thought of like a folder structure with the parent folder on the right and each subsequent child folder to the left, each separated by a dot.
TLDs (stands for 'Top Level Domain') are right at the top of the folder hierarchy. Traditionally these denote the country which the website represents, although accuracy of this is usually not enforced. There are also a number of generic top level domains such as .net .org .edu which are not tied to a location.
Some TLDs you might recognise include:
Commercial organisations operating world wide
Commercial organisations operating primarily in the UK.
Organisations and charities operating world wide
Organisations and charities operating in the UK
Universities and colleges in the US. The use of these is regulated by the US Department of Education.
Universities and colleges in the UK. The use of these is regulated by the UK Secretary of State and JISC.
You will notice that several of these have the country identifier of .uk. This is an internationally agreed country code defined by the International Standards Organisation (ISO) in ISO 3166-1. You may have seen .fr (French), .de (Germany) or .au (Australia) as other examples.
The easiest way to find these two letter codes is either to Google ‘2 letter ISO country code for [place]’ or check this Wikipedia article. This information is really useful in Google Analytics to track down elusive referral traffic – for example is traffic from Google.ie useful? Yes, if you have customers in Ireland.
New TLD codes are being created all the time, but the credibility of these are still unproved. Unusual TLDs you might have seen include .biz, .church, and .club. The important organisation here is ICANN – the Internet Corporation for Assigned Names and Numbers – who regulate TLDs, WHOIS and domain name transfer protocols internationally. NOMINET looks after transfers in the UK on behalf of ICANN.
What’s important for Search Engines?
If you are primarily targeting customers in the UK then having a .uk TLD is a huge signal about your intended market to Search Engines. You’re much more likely to show up in the results pages for your prospective UK based clients if you have .uk as the end of your domain. Aside from country level TLD being a good signal, Google says it doesn't prefer one set of TLDs over another.
What’s important for everyone else?
Our guess is that until they become more commonplace, people might be slightly put off by TLDs such as .travel or .horse because they’ll want to add .uk or .com to them and might end up so confused they give up completely. For example, how often will you bother type a domain name that ends in .tv? And .tv has been around for ages (and makes the people of Tuvalu quite a few quid). Time will tell which ones take off as well as something as popular as ".ly" (Libya’s TLD used by Bit.ly).
Want to know more about URL and their impact on SEO and User Experience? Get your reading hat on for: The Anatomy of a URL