The World Wide Web is based on unique numbers called IP addresses and every device or site that is a part of the Web contains such an address. It is pretty difficult to remember to visit 126.96.36.199 to open a website though, so a much simpler system was made in the 1980s - domain names. Each and every domain is made of a main part plus an extension, for instance domain.com or domain.co.uk. A plethora of extensions exist globally - part of them are given to countries, just like .co.uk in the abovementioned example, which is assigned to the United Kingdom, while many others are generic, for example .com or .net. Many extensions are available for registration by any entity and others have particular requirements - business registration, local presence, etcetera. You can get a new domain name from a registrar company such as ours and if the extension supports domain transfers, you are able to move an existing domain name between registrars too.