The standard Internet user will open up their browser, type in a domain name, and visit a site. Almost always this works perfectly, and they don’t realize the incredibly complex system that keeps this going. DNS (domain name system) is what matches up a domain name with an IP address. A problem with DNS can cause sites to be down. If an ISP has a DNS problem, it is possible that all of their customers will be unable to visit any site.
Most people don’t need to learn about DNS, but if you are interested, a good place to start is the Men & Mice’s DNS Glossary. There are 91 terms defined. Each entry links to other entries where appropriate, and also provides a See also… section for related topics.