Guide to Understanding Domain Names

When you use your web browser to surf the Internet, you surf from one “Domain” or website, to another. Every web browser has a textbox near the top of it called an “Address Bar” and this textbox displays the URL (uniform Resource Locator) of the domain you’re presently viewing.

For example, if you’re doing a search at Google, then it might look like this - http://www.google.com, where google.com is the actual domain name.

A domain name is like an address – it tells the computers that direct traffic around the Internet, how to find it. These computers actually look up the domain name and then translate it to an IP Address that looks something like this – 213.45.32.124 – sort of like an Internet Zip or Postal code.

Because IP Addresses are very difficult to remember, using “Real” names is far easier. Imagine if you will that you had to remember all of your friends names by their telephone number. It would get very difficult to remember all of them because numbers are so much more easily confused than words.

Also, because of the way the entire DNS (Domain Name Server) system works, it allows more than one domain name to be assigned to the same IP Address – this allows far more efficient use of the limited number of IP Addresses available.

Domain names are divided into 3 parts and are listed backwards from right to left in any URL. The TLD (Top Level Domain) is actually the extension on the right hand side, such as .com or .net and so on. Originally, the purpose of TLD’s was to clearly divide domain names into broad, yet logical areas of common knowledge.

For example, .com was originally for COMmercial organizations and .net was for NETwork infrastructures, while .edu was reserved for post-secondary level EDUcational organizations. While some TLD’s, like .edu and .mil (US MILitary) are still reserved, many are now unrestricted.

Today of course there are also numerous other TLD’s including 2 letter TLD’s reserved for each country. In Greece for example, the TLD is .gr and in Russia, it’s .ru and so forth.

The SLD or Second Level Domain is actually the name of the website, such as Google or Incansoft (one of my own domains). By pairing the SLD and TLD, it tells the DNS system what address you’re actually looking for. This is typically referred to as the Root or Root Domain.

Third Level and higher domains are the names to the left of the domain name. While calling them a Third or Fourth Level Domain is somewhat archaic, today we simply refer to these as sub-domains or sometimes vanity names. Sub-domains are controlled by the registrant (yourself for example) of the actual domain name and can be virtually anything you want.

Using Google as an example sub-domains appear like this:
 
   - http://adsense.google.com
   - http://adwords.google.com
   - http://mail.google.com

Sub-domains allow the organization to further break down the web site into logical sub-groups of specific interest or functionality and are generally treated as separate domains altogether.

So there you have it - domain names are not at all complicated to understand. While the underlying technology is obviously more complex, everything described here is all you'll really need to know about them!


The official source of Understanding Domain Names is
the Network Information Centers (NICs) page at Business.com