We’ve all heard of web addresses ending in .com, .net and even .info but what are they and what do they do?!

First off, we need to understand how computers on the internet work.

The Tubes of the Internets Are Clogged!

Every device (read: computer, fax machines, copiers) that is connected to a network, whether it’s your home or office network or the internet itself, has an address. It’s a eight to 12 digit number like 71.154.24.169

It might help to think of the phone system: Every phone has a phone number right? Well, every computer has an Internet Protocol Address. When you want to make a phone call, you pick up the phone, dial the number, wait for the other party to answer, and begin your conversation. That’s the way two computers communicate: You enter an address, i.e. www.google.com (that’s the phone number), you wait for website’s server to answer and the two computer’s have a nice chat! They can talk about webpages, FTP request, send email and much more!

Is That A Domain In Your Pocket . . .

So what does this domain business have to do with the internet? When you want to view the headlines at usatoday.com, it’s a lot easier to type in the name rather then the address: 209.97.46.5! Web address (offcially URL or Uniform Resource Locator) are aliases for that computer’s address – just like voice dialing on your cell phone, you can pick up your cell and say “Dial Jenny” and the phone dials 867-5309.

Now, technically, there is a lot more going on then what I have described here but this is basically how it all works.

Currently the governing body of domain names and internet protocols, the Internet Corporation For Assigned Names and Numbers (ICANN) has three different categories of domain names: country code top-level domain (ccTLD), generic top-level domain (gTLD) and infrastructure top-level domains.

Country Code Top-Level Domains (ccTLD)

These are used by a country or a dependent territory. It must be two letters long, for example .jp for Japan or .uk for the United Kingdom. There are currently over 243 country code domains! Click here for a list that includes the countries full name.

Generic Top-Level Domains (gTLD)

These are intended to be used by types of organizations, i.e. .com for commercial organizations. It has to be three or more letters long. Most are available worldwide, but .mil (military) and .gov (government) are restricted for the United States. gTLDs have two subclasses:

  • sponsored top-level domains (sTLD). They are .aero, .cat, .coop, .jobs, .mobi, .museum, .pro and .travel
  • unsponsored top-level domains (uTLD). They are .biz, .com, .edu, .gov, .info, .int, .mil, .name, .net and .org

There is an extensive list here, which includes descriptions of each – including official, proposed, retired and more.

Infrastructure Top-Level Domains

These are meant to be used Internet-infrastructure purposes only. The top-level domain .arpa is the only officially confirmed one. There is a rumor that .root is out there, but it’s not officially acknowledged.

Is That All?

Well, no. There is a lot more going on out there on the internets – I didn’t even cover how DNS works! There are different communications protocols (HTTP, FTP and TCP/IP to name a few), communication layers (Application, Transport, Data link, etc.) and so much more – but those are topics for another day!