@koykoy
If your baby is born in Australia, and at least one parent is an Australian permanent visa holder or Australian citizen, your baby is an Australian citizen by birth. No Australian visa is required for this baby.
If your baby is born in Australia and neither parent is an Australian citizen or permanent visa holder, your baby will generally automatically acquire the visa of either parent dependent on whichever visa is more “beneficial”.
If your baby is born outside Australia, and at least one parent is an Australian citizen otherwise than by descent, your baby is eligible for Australian citizenship by descent.
If your baby is born outside Australia and at least one parent is an Australian citizen by descent and that parent was present in Australia lawfully for at least 2 years before your baby’s citizenship registration, your baby is eligible for Australian citizenship by descent.
If your baby is born outside Australia, and neither parent is an Australian citizen, your baby has no immigration status in Australia and will need a visa to enter Australia.