Trade allows people, firms, and countries to specialize in what they do relatively well and exchange for the rest. That specialization can increase total output and create mutual gains even when one side is more efficient in absolute terms.

In practice, trade also creates tensions around jobs, dependence, and national policy. But the core economic insight remains: exchange can expand prosperity by letting effort flow toward comparative advantage.

Reference:

Wikipedia: International trade

https://en.wikipedia.org/wiki/International_trade