Name servers are adept at retrieving data from the domain namespace. They have to be, given the limited intelligence of most resolvers. Not only can they give you data about zones for which they’re authoritative, they can also search through the domain namespace to find data for which they’re not authoritative. This process is called name resolution or simply resolution.
Because the namespace is structured as an inverted tree, a name server needs only one piece of information to find its way to any point in the tree: the domain names and addresses of the root name servers (is that more than one piece?). A name server can issue a query to a root name server for any domain name in the domain namespace, and the root name server will start the name server on its way.
The root name servers know where there are authoritative name servers for each of the top-level zones. (In fact, some of the root name servers are authoritative for the generic top-level zones.) Given a query about any domain name, the root name servers can at least provide the names and addresses of the name servers that are authoritative for the top-level zone the domain name ends in. In turn, the top-level name servers can provide the list of name servers that are authoritative for the domain name’s second-level zone. Each name server queried either gives the querier information about how to get “closer” to the answer it’s seeking or provides the answer itself.
The root name servers ...