What is a reservation and what are the types?

Reserved words are the minimum required words designated to manage domain addresses stably and prevent user confusion, and are words whose registration is prohibited.

-String of 2 letters or less: a, 1, a1, ab, etc.

-String consisting of only numbers and hyphens: 12345, 12-34, 011-9934-1234, etc.

-Slang: fuck, asshole, etc.

-Existing 2nd level public domain name: co, or, re, etc.

-Words and strings required for gTLD and Internet address resource management: aero, biz, edu, info, etc.

-City, province, county-level administrative district names: Andongsi, Ansansi, etc.

-Government-related words: government, republicofkorea, southkorea, etc.