The domain name system or DNS, is a system for translating domain names like
phoenixweb.com.au (which make sense to a human), into IP addresses like
220.127.116.11 (which make sense to computers).
A common metaphor is that the DNS is like a phonebook for the internet. Unlike a phonebook however, you do not manually look up the IP address that corresponds with a certain domain name – the computer does it for you. Most commonly it is your web browser or email program which looks up the DNS entry.
The primary purpose of the DNS is to make the internet more useful, as remembering a domain name for a website is much easier for a human than remembering an IP address. Another reason to abstract the location of a website like this is that IP addresses are frequently changing. Every networked device on the internet has its own unique IP address. So when you move your website from one server to another, the IP address it is located at changes. Without the DNS, a visitor to your website would have to be informed of this change. With the DNS, we simply change the IP reference for the domain name, making the move seamless to website visitors.
When you tell your browser to visit a website on the internet, first it must work out where the website is located (the internet is a big place after all). Your browser contacts a special kind of server called a DNS server and relays the domain name. The DNS server searches itself and the DNS system, then sends back the DNS record for that domain; which includes the necessary IP address. The browser then sends a request to that IP address, which is received by the server hosting the website. This process takes about 500 milliseconds.
The process is described in more detail in our DNS name server entry. You can read more about the domain system at the How Stuff Works DNS web series and NetRegistry’s DNS article.