Domain names consist of individual labels separated by dots, for example: mydomain.A Fully Qualified Domain Name (FQDN) uniquely identifies the hosts position within the DNS hierarchical tree by specifying a list of names separated by dots in the path from the referenced host to the root.For example, the DNS domain name registered to Microsoft () is known as a second-level domain.This is because the name has two parts (known as labels) that indicate it is located two levels below the root or top of the tree.Any DNS domain name used in the tree is technically a domain.
DNS originated in the early days of the Internet when the Internet was a small network established by the United States Department of Defense for research purposes.
DNS Domain Name Hierarchy The previous figure shows how Microsoft is assigned authority by the Internet root servers for its own part of the DNS domain namespace tree on the Internet.
DNS clients and servers use queries as the fundamental method of resolving names in the tree to specific types of resource information.
The host names of the computers in this network were managed through the use of a single HOSTS file located on a centrally administered server.
Each site that needed to resolve host names on the network downloaded this file.