The Format Of A Domain Name

Like a physical address, Internet domain names are heirachical (only a little more strict), so while your address might look like:

House name: 3 Willow Walk
Town: Trumpton
County: Trumptonshire
Country: England

An Internet domain name looks like:

Host name: www
Domain: gondolin
Second level domain: org
Top-level domain: uk

As with physical addresses, the exact layout can vary. Sometimes there will be more parts to the address, so in the same way that houses can be divided into multiple flats or apartments, domains can be divided into multiple subdomains (there could be a domain name like "www.testing.gondolin.org.uk" for example). Sometimes there will be fewer parts - typically the larger the organisation, the shorter their domain name, ibm.com for example.

At the moment, there are only a few top-level domains, but that's all about to change fairly soon. The main ones currently are:

You may notice the word "historically" quite a lot, above. That's because as the Internet grew more popular, the original restrictions became harder to enforce (and possibly unnecessary). In the 1990s if you wanted a .net domain you had to prove you were a network provider, but now anyone can get one.

Useless trivia: The "uk" country code should be Ukraine and Britain should be using "gb", but for historical reasons Britain uses "uk" (United Kingdon) and Ukraine ended up with "ua".

Second level domains aren't quite so restricted (you can have pretty much whatever you like under "com", "org" or "net"), although typically each country has its own version of "com", "org" and "net" and the actual domain lives under that (the UK has "co.uk" and "org.uk" for example)