Computers on the internet communicate via TCP/IP (Transmission Control Protocol/Internet Protocol). When a computer tries to communicate with another machine it looks up the IP address assigned to the name you type in the URL. The actual letters you use are meaningless to the computer until they are translated into an IP address.

Here is a simplified view of what happens when someone types www.yourcompany.com into their browser:

Your computer checks its TCP/IP configuration for its Domain Name Server address list. It queries that computer's database for the IP address of the fully qualified domain you typed in. If it is not found, you get routed to the root servers in the path of that DNS server. If they don't have the address, you get routed to InterNIC's root servers which match up the second level domain name to the Primary and Secondary DNS servers that hold the Start of Authority record for the domain. That Name Server has the IP address of the Fully Qualified Domain Name. Now the DNS servers send the information backwards to all of the requesting servers so they now know the path, and you don't bounce around so much next time.

A full understanding requires at least one book. A good starting reference is DNS and BIND published by O'Reilly & Associates, Inc.

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