A classic carry trade borrows yen at near-zero rates to hold Australian dollar assets at higher rates. The investor earns the interest-rate difference as long as the Australian dollar does not fall by more than that.
Why it matters
Carry trades build up in calm times and unwind suddenly in shocks, when investors rush to repay the borrowed currency. That is one reason the Australian dollar can fall sharply in a global sell-off.
See the data: AUD/JPY.
General information, not advice.