How do prisoner swaps work?

After 804 days in jail in Iran, Australian academic Kylie Moore-Gilbert is finally free. The Iranian government says it's the result of a prisoner swap, but the Australian government isn't confirming anything. So what do we know about the secretive world of prisoner exchanges? And if Iran got what it wanted, will it lead to more hostage diplomacy? Featured: Dr Rodger Shanahan, Research Fellow, Lowy Institute