Short for Domain Name System or Domain Name Service, a DNS is an Internet or network server that helps to point domain names or hostnames to their associated Internet Protocol address and was introduced by Paul Mockapetris and Jon Postel in 1983. Without a DNS to resolve a domain name or the proper rights, users would have to know the IP address of each of the web pages or computers you wanted to access.
Tip: DNS uses port 53.
How does it work?
When a user wants to visit Computer Hope, they can type "http://www.computerhope.com" into the address bar of their browser. Once that domain name has been entered, it is looked up on a Domain Name System where it is translated into an IP address that is more easily interpreted by a computer, e.g. 126.96.36.199. Using that IP address, your computer can then locate the Computer Hope web page and forward that information to your browser. Below is a visual example of how DNS works.
As seen above, not every DNS stores every address on the Internet. If a domain name is not found, the server may query other domain servers to obtain its address.
What is the hierarchical structure of DNS
There are millions of websites available on the Internet to make finding an address the domain naming is broken into a hierarchical structure. Below is how DNS is structured on the Internet and an example of three different addresses.
In the above example, all websites are broken into regional sections based on the top level domain (TLD). In the example of http://support.computerhope.com it has a ".com" TLD, with "computerhope" as its second level domain that is local to the .com TLD, and "support" as its subdomain, which is determined by its server.