Australia is a country in southern hemisphere, officially Commonwealth of Australia, comprises mainland of world's smallest continent and major island of Tasmania . It has numerous other islands in Pacific and Indian Ocean . Neighboring countries are East Timor, Indonesia, Guinea to north, Solomon Island, New Caledonia to northeast, Vanuatu and New Zealand to southeast. 40,000 years before a European settlement commenced in last 18 th century, mainland of Australia and Tasmania were also inhabited by 250 individual nations of the Australians.