Page "Domain Name System" Paragraph 2

The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name servers for each domain.

Authoritative name servers are assigned to be responsible for their particular domains, and in turn can assign other authoritative name servers for their sub-domains.

This mechanism has made the DNS distributed and fault tolerant and has helped avoid the need for a single central register to be continually consulted and updated.

Additionally, the responsibility for maintaining and updating the master record for the domains is spread among many domain name registrars, who compete for the end-user's, domain-owner's, business.

Domains can be moved from registrar to registrar at any time.