.cn, as the country code top-level domain (ccTLD) for the People's Republic of China, is managed by a branch of the Ministry of Industry and Information. The registry is maintained by China Internet Network Information Center (CNNIC).
The registry has created a set of predefined second-level domains for certain kinds of organizations and geographic locations. Any individual may register for second-level domain names under these conditions.
Here are some examples: ac.cn is for academic and research institutions, com.cn is for industrial, commercial, financial enterprises, and individuals. edu.cn is for educational institutions (usually universities and colleges).
Here are also examples for geographic locations: sh.cn is for Shanghai Municipality. bj.cn is for Beijing Municipality. tw.cn is for Taiwan Province.
.cn ranks #3 among all domain extensions, and #1 among all country-code extensions (ccTLDs). Currently, there are 12.7M registered .cn domain names. CNNIC is the current registry of .cn extension.