The Internet communicates between devices that are assigned numbers called IP addresses, think of them like phone numbers. Each and every device on the Internet is assigned an IP address number.
Let's look at a particular example. Using the tool "ping" in Windows Command Prompt or Terminal in MacOS or Linux we can ping google.com
PING google.com (188.8.131.52) 56(84) bytes of data.
We can see here that Google is at 184.108.40.206, using some mathematics beyond the scope of this article this number is 2398766830 and we can get to Google via https://2398766830,
Obviously remembering 2398766830 in order to search the Internet is not convenient and this is where domain names come in.
Domain names are like an address book for the Internet provided by DNS, the domain name service. Domain names are read from right to left, with the rightmost known as a Top Level Domain (TLD) and the names left of that are subdomains. Once upon a time domain names were free but now they need to be purchased and registered.
Domains are registered and managed by DNS servers. Tools such as email clients and web browsers know how to talk to DNS servers to eventually find the address of something on the Internet.
Let's use this site as an example, blog.azegia.com.au. On the right of the address we see "au" which means it's managed by Australia. Next we see "com" which means it's a company in Australia. After that we see "azegia" which is a registered domain name. "azegia" is therefore a sub domain of "com.au". Using an online "whois" tool we can see that "azegia" was registered with GoDaddy but also the "azegia.com.au" is managed by DNS server "n1.syd03.hostingplatform.net.au" which is a DNS server run by VentraIP in Sydney.
In short this means "azegia.com.au" was purchased from GoDaddy and the DNS for "azegia.com.au" is managed by a server belonging to VentraIP. An important point here is that buying a domain name requires the domain name to point to a DNS server. In the case of "azegia.com.au" it could use GoDaddy's DNS servers but it's using VentraIP's instead. This is useful in that if VentraIP becomes an issue, a different DNS server can be used and GoDaddy can be told to redirect to the new DNS server.
Let's look further into the example of "blog.azegia.com.au". "azegia.com.au" is running a web server and other things and going to "azegia.com.au" in a web browser will bring up a web site. However on "azegia.com.au" managed by Ventra IP the subdomain "blog" has been set up to point to Google's Blogger. Blogger has been configured to know which blog "blog.azegia.com.au" is pointing to and will bring up the correct blog when accessed.
This great because the DNS server for "azegia.com.au" can be set up with subdomains that can point to different parts of the Internet and it looks legit and professional.
There are three steps to getting and using a domain name, these are:
To find a domain name, use these two services, ICANN (international) and AUDA (Australia). You should use these because they are governing bodies and not commercial businesses. They won't try to sell you anything or modify prices based on your interest, not that you can buy from them anyway.
After that configure configure the domain you just purchased to point to two or three DNS servers. Multiple DNS servers are registered in case the primary one fails and in that event the secondary or tertiary server can be used.
This should give you a basic understanding of why domains are useful, what they can do, how to find an used one, how to purchase one, and a starting point on how to put it to use.