A trade war happens when countries try to hurt each other's economies by making it expensive or difficult to buy goods from one another. The main weapon in a trade war is the tariff, a tax added to products crossing borders. If Country A puts a 25% tariff on steel from Country B, that steel suddenly costs much more, making it harder to sell.

Trade wars usually start when one country believes another is treating it unfairly. Country A might think Country B isn't buying enough of its products or is cheating somehow. So Country A adds tariffs. Country B gets angry and adds its own tariffs in response. Back and forth they go, each trying to pressure the other to back down.

The term war fits because both sides get hurt, just like in a real war. Tariffs make products more expensive for regular people in both countries. A tariff on imported fruit means families pay more at the grocery store. A tariff on manufacturing materials means factories might close and workers might lose jobs. Companies that buy and sell internationally watch their profits shrink.

History shows that trade wars rarely have winners. The most famous example, the Smoot-Hawley Tariff Act of 1930, made the Great Depression much worse by triggering retaliatory tariffs worldwide. Modern countries usually try to resolve trade disputes through negotiation instead, because even though trade wars sound dramatic, they mostly just make everyone poorer.