Carry trade
Buying a high-yield currency and selling a low-yield one to collect the interest differential.
Classic: long AUDJPY when Aussie rates are high and Japan is near zero. Works until it doesn't - carries unwind violently when risk sentiment sours. Months of swap income can be lost in a weekend gap.
Related
Learn to actually use Carry trade.
Definitions are the easy part. The free first five modules put this on a real chart and make you do the work. No card required.