Tariff

A tax levied on goods imported into a country, i.e. a 10% tariff levied on an imported car priced at $20,000 would increase the price to $22,000.

Quota

Specifies maximum amounts of goods that can be imported in any period of time.

Subsidy

A subsidy is a payment made to a producer, i.e. The Wool Act, in 1990 had a subsidy rate of 127 percent. The farmer who got $1000 for selling wool in the market would receive an additional payment from the government of $1270.