Domain Name System
name service switching
(DNS) A general-purpose distributed, replicated, data query service chiefly used on Internet for translating hostnames into Internet addresses. Also, the style of hostname used on the Internet, though such a name is properly called a fully qualified domain name. DNS can be configured to use a sequence of name servers, based on the domains in the name being looked for, until a match is found.
The name resolution client (e.g. Unix's gethostbyname() library function) can be configured to search for host information in the following order: first in the local hosts file, second in NIS and third in DNS. This sequencing of Naming Services is sometimes called "name service switching". Under Solaris is configured in the file /etc/nsswitch.conf.