When you type in a web page URL into your browser to pull a site the first thing the computer does is take that DNS hostname such as "google.com" and translate it into an IP address.

In order to determine the IP address of google.com the machine must first find out who has the authority to tell you what IP address google.com is.

This job is handle by the Root Name Servers the tell the client what DNS server has authority over the domain name you wish to look up. Take a look at the following query performed on the A record for google.com:

How I am searching: Searching for google.com A record at d.root-servers.net 128.8.10.90: Got referral to M.GTLD-SERVERS.NET. (zone: com.) took 9 ms Searching for google.com A record at M.GTLD-SERVERS.NET. 192.55.83.30: Got referral to ns1.google.com. (zone: google.com.) took 355 ms Searching for google.com A record at ns1.google.com. 216.239.32.10: Reports google.com. took 77 ms

Response:

Domain Type Class TTL Answer google.com. A IN 300 72.14.207.99

As you can see above the first thing it does it contact the root servers in this case it is "M.GTLD-SERVERS.NET". M.GTLD-SERVERS.NET tells the client that the authoritative name server (meaning who has control of) for google.com is ns1.google.com or 216.239.32.10. Then ns1.google.com tells you that the IP for google.com is 72.14.207.99. Now that you machine knows the IP address for google.com it can communicate directly to that web server and request the google.com homepage.