A word of warning!
The DIBP is now the DoHA and the website is not accurate and should be taken with a grain of salt. Many people think that if they phone or email the immigration department the answers they get will be correct.
Strangely the staff are not qualified to answer your questions, nor are they accountable for the often fatal information they give regarding applications.
Your applications are processed by Case Officers and they use "the regulations" and PAM 3 guidelines in processing applications. The Regs are online but PAM 3 is a bit harder to access - a subscription is available for around $700 per year.
To get accurate advice on visas you need to contact a Registered Migration Agent (preferably Australian based), not all of these are created equal - so do your research.