Inter-market analysis is the study of how all different asset classes are performing and how they affect each other.

Many currencies are correlated and move in the same direction most of the time, but also, seemingly unrelated markets do the same.
When different markets are moving in the same or opposite direction as they normally do, you can use the movements in one market to confirm or even predict movements in another.
Example, AUD is very much affected by China economy. Also, you can check out the commodity index(CRB) and copper when looking for opportunity at AUD.
http://stockcharts.com/h-sc/ui?s=$CRB
https://www.investing.com/commodities/copper

Divergences from Normal Correlations.
When markets that normally trend in the same direction start to diverge, those trend divergences are often leading indicators of changing market conditions.