Domain extensions or TLDs are categorised into groups. The original gTLDs (generic top-level domains) included .com, .org, .net, and .gov, and over time the list was expanded to include ccTLDs (country code top-level domains) like .uk, as well as more specific geographic domains like .london, .wales and .scot.
The list of gTLDs has grown to include professional domain extensions like .photography, .restaurant and .shop, as well as new TLDs like .ninja, .lol and .love.
Different extensions suit different purposes. For example, if your website is aimed at a UK audience, it makes sense to choose a .co.uk domain. If you want your website to have international exposure, consider registering the same domain name with .eu and .com extensions. Securing your domains with as many available extensions as possible is the best way to reach the widest audience.