Domain Name System (DNS) is a database system that translates a computer's fully qualified domain name into an IP address.
Networked computers use IP addresses to locate and connect to each other, but IP addresses can be difficult for people to remember. For example, on the web, it's much easier to remember the domain name www.ebay.com than it is to remember its corresponding IP address (220.127.116.11). DNS allows you to connect to another networked computer or remote service by using its user-friendly domain name rather than its numerical IP address. Conversely, Reverse DNS (rDNS) translates an IP address into a domain name.