When a fund/ETF has a "domicile" of Australia it means it is a registered fund in Australia for tax purposes.
That means, investors who buy into this ETF should not have to fill in or file additional tax or legal documents with the ETF issuer.
However, this information changes regularly and can be wrong, so you should always read the Product Disclosure Statement (PDS) to learn where your chosen ETF is domiciled. Then consult a financial adviser and tax agent. They will be able to tell you what this information means, if you're still confused after reading the PDS.