NCLEX is new in Australia and is called MCQ here, but it has been used in many countries including U.S for decades now and it is a very good testing system that serves only one purpose : to determine if it is safe for you to begin practice as an entry level nurse.
If you are an internationally qualified nurse, who wants to become a Registered Nurse in Australia, there are certain steps you need to follow to gain that registration. It will depend on a few factors, but your qualification and your ability to show that you can meet the Australian registration standards are the two most important factors.