Think of DNS as a kind of phone book for the Internet. If you have a person's name, but do not know their telephone number, you can look it up in a phone book. DNS provides this same type of service to the Internet. When you visit 'http://www.google.com' in a web browser, DNS retrieves the site's IP address, '72.14.207.99', which the browser then uses to connect to the webserver.
Without phone books, you would not be able to learn someone's telephone number unless they previously gave it to you. Likewise, without DNS, you would only be able to reach sites via their IP addresses; instead of 'www.google.com' or 'www.google.com', you would have to type 'http://72.14.207.99' every time you wanted to view the sites.
