A lot of people don’t understand (or don’t care) why some domains start with www and why some domains do not. Well let me shed some light on the matter.
Technically speaking www.example.com is just a subdomain of example.com, which is the ‘root’ domain. Just like mail.google.com is a subdomain of google.com. www.example.com, in theory, could have totally different content to example.com (just as mail.google.com has different content to google.com). However in the vast majority of cases they both show the same content, because lots of people assume the www is optional. So why the www? Well according to Wikipedia it was accidental.
Now because people assume the www is optional it’s defiantly a good idea to point both to the same site. It’s also good SEO to choose one domain and redirect the other. I.e. redirect www.example.com to example.com or visa versa. You see Google doesn’t like exactly the same content appearing on multiple sites (duplicate content). People used to steal (AKA scrape) content and put it on their own sites in order to increase their Google ranking. So now Google punishes people who have duplicate content. Now remembering that www.example.com and example.com are technically different domains if you don’t redirect Google will see it as duplicate content.
At the end of the day its your decision if you want your domain to be www.example.com or simply example.com, just make sure you redirect! We decided on just digitalgas.com.au (I always prefer to drop the www) so have a look what happens to the address box when you go to www.digitalgas.com.au (for those paying attention the www disappears).