Every website has an IP address that allows users to connect to the server that stores the website. A typical IP address is a long set of numbers, such as 74.125.228.232. Because most humans cannot remember complicated numbers, the World Wide Web uses DNS as a type of address lookup service, similar to a phone book or the contact list on a smartphone, where the IP address is listed alongside one or more names for a given website.

When users enter the name of a website (such as Google.com or BarnesAndNoble.com) in their browser’s address bar, the browser connects to a DNS server to look up the IP address associated with that name and then uses that address to connect to that server. This is similar to using the contact list in a cell phone to call a friend instead of dialing the number directly. Just as with a phone number, users can enter the Web server's IP address number directly into the browser’s address bar without going through DNS.

The DNS also ensures that no two websites have the same name, and the Internet Corporation for Assigned Names and Numbers (ICANN) controls and assigns the names themselves.