The Australian Government has a strong immigration policy which is modified and adapted to match changing economic conditions. Except under very rare circumstances no non-Australian may enter Australia without a valid visa.
This applies to tourists, business people, temporary and permanent immigrants.
There are a number of categories under which a person may be granted a visa, ranging from a simple tourist visa to one granting permanent resident status. Visas may be granted outside Australia or onshore depending on the criteria required at the time of application.