The whole database can be pictured as an inverted tree, with the root at the top. Each node in the tree represents part of the overall database, called a domain. The top-level domains divide the Internet domain space organizationally. In addition, a top-level domain exists for each country. Their domain names follow ISO 3166, an international standard defining a two-letter abbreviation for every country in the world.
Examples are .au for Australia and .
Indicates authority for the domain data. NS Name server. Lists a name server for the domain. TXT Textual information. RP Responsible person.