DNS is probably the most broadly used network service today, yet to most DNS users the service is completely transparent. The most common use for DNS is navigating to a web site. Whether you go to a site by typing the site name in browser or by clicking on a link, the first stop is a DNS server. Computers use numerical IP addresses, not canonical names to find other computers. People are much better at remembering names than numbers. DNS servers translate the name used for network device, such a web server, to an IP address for that server. From there IP routing and a few other technologies connect you to the server. It all sounds simple, but here is an analysis of the DNS resolution for Microsoft.com from my desk using SolarWinds Engineer's Toolset DNS Analyzer tool.
As you can see, there is a lot going on. Microsoft wants to make sure that people can always access their site. So they have implemented multiple name servers with multiple paths to two authoritive addresses for Microsoft.com. Compare the DNS map above with the results of an nslookup below done from the same PC.
...and the results of a trace route from my PC.
What we see is nslookup locating the two addresses to Microsoft and the ping tracerout finding a path through the Internet to Microsoft. Microsoft chooses to configure their web server to not respond to ping, so that is where it times out. This is not an unusual practice.
DNS has many other functions including reverse DNS where an IP address is translated to a name. As a former network engineer, I prefer to use IP address rather than DNS names where possible. The problem with continuing that practice is the rapid adoption of IPv6 addresses. Google's IPv6 Address is 2001:4860:4860::8888, and that is an abbreviated address!
The bottom line is the more you know about DNS, the more you understand how critical it is. Check out our other tools for DNS, including many free ones, at DNS Stuff