What are tariffs? Here's everything you need to know about the import duties.

President Trump, an avowed fan of tariffs, is set on Feb. 1 to unleash a wave of new import duties on America's three closest trading partners — Mexico, Canada and China. 

Although tariffs are a bane to most economists, they are a widely used as a tool for regulating international trade and for shielding domestic industries from foreign competition. At the simplest level, tariffs are taxes placed on goods made overseas that are imported into the country. Notably, foreign companies aren't responsible for paying the duties. Instead, U.S. businesses directly pay the tariffs on their imported goods to the federal government, according to the Tax Foundation, a tax-focused think tank.

Because American businesses are on the hook for paying the tariffs on imports, they historically have passed on some or all of those costs to consumers. At the same time, tariff proponents like Mr. Trump argue that such levies can help protect manufacturers here at home. For instance, consumers may opt to buy U.S.-made products rather than newly pricier imports, while companies may choose to avoid tariffs by opening new plants in the U.S.