Business income is the net income you receive from carrying on a business. It is assessable income and the ATO requires that you report it on your tax return. Business income includes income you make as a sole trader (self-employed), partnership income, and trust income.
Income earned as a sole trader is reported on a separate business schedule attached to your tax return. For partnership income, each partner must report their share of the partnership’s net income and pay tax on it. Trust income is taxable to the beneficiaries who are entitled to receive that income and must report it on their returns. If you run your business as a company, that income is likely classified as salary, wages, directors fees, dividends, etc. and should be reported on your return in the relevant areas.
Note that business income is distinct from employment income, which you earn primarily through salaries and wages.