Carry trade
A strategy of borrowing a low-interest currency and investing in a high-interest one to earn the rate differential; it unwinds quickly in risk-off periods.
The classic example: selling the yen (low interest) to buy the dollar or the Mexican peso. The position earns positive swap every day, but when the yen suddenly strengthens, the currency loss can wipe out years of interest income (as in the August 2024 unwind).
For retail traders, carry is less a strategy on its own than a principle of picking the swap direction that works in your favor on the positions you carry.