Before we start - what is a tariff?published at 13:44 Greenwich Mean Time 5 March
In short: tariffs are taxes charged on goods imported from other countries.
The companies that bring the goods into the country pay the tax to the government.
Typically, tariffs are a percentage of a product's value. Imposing a 20% tariff on Chinese goods means a product worth $10 would have an additional $2 charge applied to it.
Firms may choose to pass on some or all of the cost of tariffs to customers.
The BBC's Adam Fleming explains what a tariff is