Yes, Australian residents must declare and are taxed on their worldwide income. You must declare all of your income, no matter what the source. Foreign income includes foreign pensions and annuities, foreign employment, foreign investment, foreign business, and capital gains on foreign assets.
Foreign income may very well be taxed in the foreign country where it originated. In order to combat double taxation, there are a series of credits and exemptions - thanks to the Australian government’s tax treaties with more than 40 countries - that should help you get some of that money back.
If you are not an Australian resident, then you may not have to declare your income from non-Australian sources.