A country code top-level domain (ccTLD) is an Internet top-level domain which generally reserved for a particular country to use to serve their community.
You can recognize all country domains by the two letters long extension, so if you see a two letter top level domain you can be sure it's a Country Domain.
Nearly every country in the world has a corresponding ccTLD. With registering a ccTLD, you can show your audience where the site is based and who it targets.
Be aware that most ccTLDs limit registration to individuals and companies located in their country. There are only a few countries allowing domain registration to anyone in the world.
You can search here for all ccTLDs by region and find out more information about your specific country and its domain.