translation of a domain name by software (name resolver) into an equivalent IP address
Host name is said to resolved to an address.
In Unix, name resolver uses gethostbyname routine.
Each resolver is configured with the address(es) of a local domain name server(s).
When a DNS request contains a name for which a server is an authority, the server answers the request directly to the resolver(client).
Iterative query resolution
when a request arrives for a name server outside the set for which the server is an authority, the server becomes a client of a root server and of other servers down the hierarchy until a server which has authority for the domain is found .