dnsfaqs.com is an unbiased, comprehensive guide to the Internet's domain name system.

DNS stands for Domain Name System.  It is used to translate IP addresses into easy to recognize domain names, and is used both by humans and machines alike to direct traffic to the right location.

DNS has been around since the very early days of the Internet.  It is organized into a hierarchy resembling a rather flat organizational chart with a set of root servers at the top.

At the very top of the org chart there are 13 root servers that direct all traffic.  They are strictly traffic cops; they do not do anything else but refer other DNS servers to the right location to find the answer for a request.  As a user of the Internet you never talk to the root servers, typically only DNS servers query the root.

Just below the root servers are the top-level domain servers.  These are also referral servers and make up the top-level and country-code domains.

Below the top-level servers are all other DNS servers.  These servers are run by Internet Service Providers, Web Hosting companies, or even yourself.  These can be both caching or authoritative nameservers.

At the bottom are the DNS clients.  These clients make DNS queries such as your web browser or email program.