Short answer
You need to show that you have real access to enough money for yourself and any family members coming with you for your planned stay in Australia.
People applying for a Student visa need to show they have real access to enough money to cover costs for themselves and any family members coming with them.
Everyone applying needs to state in the application that they have enough money for the whole stay. Some people may also need to provide documents showing the amount and type of funds they have.
Evidence may include bank deposits, loans, scholarships, financial support, or annual income. The key point is real access: the money must be available to support you in Australia.