Australian domain names (ending in .au) are useful if you want to be recognised as an Australian based business.
There may be some small advantage in Google searches from within Australia too.
However, the Australian Regsitry is very strict on issuing Australian domains (.com.au, .org.au, .net.au etc). You will need to have an ABN or ACN for a relevant business or you may not be allowed to register the domain.
For a full explanation, please see the Eligibility Criteria.
Other top level domain names, e.g. .com are very much easier to obtain.
Many of our clients register multiple domain names, particularly if they wish to protect their business area from competitors.
You may add additional domain names as Parked Domains. For an full explanation please see the Hosting FAQs below.
There are now literally 100s of different domain name extensions available for you to register, have a look at the full list here.