The Domain Name System (DNS) helps users to find their way around the Internet. Every computer on the Internet has a unique address - just like a telephone number - which is a rather complicated string of numbers. It is called its "IP address" (IP stands for "Internet Protocol"). IP Addresses are hard to remember. The DNS makes using the Internet easier by allowing a familiar string of letters (the "domain name") to be used instead of the arcane IP address. So instead of typing 18.104.22.168, you can type www.internic.net. It is a "mnemonic" device that makes addresses easier to remember.
Scattered across the Internet are thousands of computers - called "Domain Name Resolvers" or just plain "resolvers" - that routinely cache the information they receive from queries to the root servers. These resolvers are located strategically with Internet Service Providers (ISPs) or institutional networks. They are used to respond to a user's request to resolve a domain name - that is, to find the corresponding IP address.