Australian English - I'm the True Blue Aussie

It's a way of expressing that I'm surprised and that I want to hear more. You can also use it as a way of verifying with someone whether or not what they've said is true so if someone has said to me say the weather was the worst I had seen in Melbourne in my entire life then I could say in return a fair-dinkum are you telling me the truth? So yeah those are the two main ways that you would use that really popular stereotype expression of Australia fair-dinksum.