There is more than one way to be interviewed.
First phone call with the recruiting agent.
In this phone call the recruiter will clarify and check you match the job description. IF you are successful, an internal interview shall be scheduled. From the 10 people making the shortlist only four to six will be invited to an internal interview. For how to prepare to your first phone call read here
The internal interview with the Agent / HR recruiter
If you pass this interview you will get your chance to an interview with the company you will be working for. A max of 3 people per agent is allowed by the client so the agent will make sure you are right. He might even help you fix your CV, give you advices on what to wear and basically from this point forward, you and the recruiting agent are a team with one aim – to get you the job! For how to prepare to your internal interview read here
First external interview.
This is what you waited for, the opportunity to talk to a real employer seeking new employees. Furthermore, you are probably sitting in front of your future direct boss or manger and an HR recruiter from the company. Less than 5 people have made it so far and this is your first real chance. For how to prepare to your first interview read here. In some occasions a single interview at the client site will be required for the employing company to give you a job offer. In some cases you will be advanced to a second interview.
Second external interview.
A second interview is when you are wanted and one of the big players in the company wants to meet you, max of 2 to 3 people have reached this point. For how to prepare to your second interview read here
The job offer
After a second interview you are most likely to get a job offer. For information on how to read an Australia job offer, what to check and compare job offers read here
If you were successful in of the above you should be moving to the job offer page to learn what does the package you were offered entails