If you decide that a company structure best suits your business, then you need to register as a company. One of the benefits to registering as a company is being able to register a company name. With a company name you have the advantage of holding exclusive rights to that name in Australia, without having to register in each state.
You can only choose a company name not already registered to a company or business. Special approval is also required to use certain words.
If your company carries on business in a name different to your registered company name, then you must register the business name.