A ccTLD is a country code top-level domain.
It is the part at the end of a domain name that is linked to a country, territory or geographic area. Examples include:
.ukfor the United Kingdom.defor Germany.frfor France.aufor Australia
Most country code domains use two letters and are based on international country codes, although each registry sets its own rules for how domains can be registered.
Some ccTLDs are mainly used by businesses and individuals in that country. Others are also used more broadly because the extension has become popular for another meaning or industry.
If you are choosing a domain for a UK business, a .co.uk or .uk domain is often a familiar and trusted option.