A trade war happens when one country retaliates against another by raising import tariffs or placing other restrictions on the opposing country's imports.

Tariffs mean tax which is imposed on the goods being imported from another country.

The trade war is done in order to protect the domestic business. So, it may start locally. The pressure which is created locally can lead to international wars like these trade wars. This, in turn, increases the demand for domestic products that means the products created locally soon will begin to get recognized and there will be a lot of opportunities for local goods...Listen for more

Sources: Investopedia, BBC, livemint, CNBC,  Times Of India.