What is DNS
The Domain Name System (DNS) is a system used to convert a computer's host name into an IP address on the Internet. For example, if a computer needs to communicate with the web server example.net, your computer needs the IP address of the web server example.net. It is the job of the DNS to convert the host name to the IP address of the web server. The DNS uses the UDP Port 53 or TCP Port 53. It is defined mainly by RFC 1034 and RFC 1035. There are later RFC which define changes to the system.