Usually when you include the dot it's called TLD or ccTLD (Top Level Domain or Country Code Top Level Domain). Country codes as in ISO 3166 are without the dot, and written with capital letters, and they predate the internet, first published in 1974. The tlds were based on these codes.
There are some minor differences, e.g United States Minor Outlying Islands (UM) and Western Sahara (EH) have a country code, but no tlds were implemented.
- https://en.wikipedia.org/wiki/Country_code
- https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2
- https://en.wikipedia.org/wiki/Top-level_domain
Edit: In the article it's correctly written as CH