The Internet was built on the notion that any computer on a global network can be identified by its numeric Internet Protocol (IP) address. But since people, and not machines, are the primary users of the Internet, a more people-friendly naming system called the Domain Name System (DNS) was invented. DNS maps a host name like www.rwgusa.com to the IP address of the machine that hosts the RWGUSA web site. For example, DNS actually maps the host name www.rwgusa.com to the IP address 188.8.131.52
DNS is built upon the notion that some server's are 'authoritative' (meaning, knows all there is to know) for certain domains. A distributed name server hierarchy, beginning with the A Root Server and ending at the thousands of nameservers active on the Internet, ensures that the naming and directing system works the same from anywhere.