DNS stands for Domain Name System. In the early days of the Internet, back when it was controlled by the Defense Advanced Research Projects Agency (DARPA), traversing the net was made possible by a manually-updated list of server names and IP addresses. When people wanted to access a server, they needed to consult this list for the appropriate server name or IP address. As this fledgling mesh of networks rapidly grew, it became apparent that the "telephone book method" of managing server name/IP address translations was unfeasible. As a result, DNS was born.
In the 1980s, control of the Internet was transferred from DARPA to the National Science Foundation (NSF), and development and refinement of DNS continued. In 1992, Congress granted NSF the right to commercialize the Internet, and the World Wide Web as we know it was born. Thanks to DNS, it was possible for companies to assign easily-remembered names like www.google.com to Web services. If it were not for the development of DNS, today's Internet would not exist.
Browsing the Web has become as common-place as making a phone call. We open up our browser of choice and we go to the Web page that we want to visit. Although this appears to be a simple task that is completed solely by your computer, it is actually a four-step process involving your computer, a DNS server, and the Web server that is hosting the Web page.
For example, when you enter http://www.alliancecom.net into the address bar of your browser and press ENTER, that information is sent across the Internet to your ISP's DNS server, where it is translated into the IP address of the Web server hosting that page (18.104.22.168). The DNS server then sends that IP address back to the computer, allowing the browser to connect to the Web server. The Web server then processes your request for the Web page and sends the appropriate content to your browser. Voila! Your computer displays the requested Web page in the blink of an eye. The diagram below further illustrates this process.
As you can see, DNS is a very simple concept made possible by a very complex global system. The intricacies of the global DNS network are beyond the scope of this document. If you would like more detail on DNS and domain names, click here.