When you visit a website like www.example.com, you use a domain name—a human-friendly address that helps you reach the right place on the internet. Domain names exist because long strings of numbers, known as IP addresses, are difficult for people to remember and use. Instead of typing 93.184.216.34 into your browser, you simply enter www.example.com. Popular domains such as google.com, amazon.com, and wikipedia.org are all mapped behind the scenes to specific IP addresses. This mapping is possible thanks to the Domain Name System, or DNS.

When you type a domain name into your browser, the first step is for the browser to ask, "What is the IP address for this domain?" The browser sends a request to a DNS resolver, often managed by your internet service provider. If the resolver does not already know the answer, it contacts an authoritative DNS server for the domain. This authoritative server holds the official mapping of the domain name to its IP address. Once the resolver gets the IP address, it sends it back to your browser, which can then connect to the correct web server. The diagram above shows this journey: from your browser, to the DNS resolver, to the authoritative DNS server, and back again with the IP address.

You can think of DNS as the internet's phonebook. In this analogy:

• The domain name is like a person's name you want to call;
• The DNS resolver is like calling directory assistance to look up the number;
• The authoritative DNS server is the official directory that holds the correct phone number;
• The IP address is the phone number you actually dial to reach the person.

Just as you don't memorize everyone’s phone number, you don’t need to remember every website’s IP address. DNS handles the lookup for you, making the web much easier to use.