Domain name management agency ICANN:
ICANN (The Internet Corporation for Assigned Names and Numbers, ICANN) is a non-profit international organization, responsible for the Internet Protocol (IP) address space allocation, protocol identifier assignment, generic top-level domain (gTLD) and the national and regional top-level domain (ccTLD) system, management and the root server system management.
the global total of 13 sets of domain name root servers. 1 is a root server, placed in the United states. The remaining 12 are supplemented by root servers, of which the 9 placed in the United States, Europe, the 2 (located in the UK and Sweden), Asia, the 1 (in Japan), by the internet name and number distribution agency ICANN unified management.
any DNS to go through these 13 root servers to get the top index, is not to say that you will access the.Com through these servers, access to.Cn will not pass through the server.
and every top domain, either gTLD (gTLDs), or ccTLD (international top-level domain), they have their own domain name server (i.e. the top-level domain, such as NS records):
and so on.