Tariff
A tariff is a tax on imports or exports between sovereign states. It is a form of regulation of foreign trade. It is a policy that taxes foreign products to encourage or protect domestic industry. It helps limit trade deficits. The tariff is historically used to protect infant industries and to allow import substitution industrialization.
Tariff in United States history
Currently only about 30% of all import goods are subject to tariffs in the United States, the rest are on the free list. The "average" tariffs now charged by the United States are at a historic low. The list of negotiated tariffs are listed on the Harmonized Tariff Schedule as put out by the United States International Trade Commission.