In customs terms, what is an "import duty"?

An "import duty" refers specifically to a tax imposed on goods that are brought into a country from abroad. This duty is primarily designed to generate revenue for the government and to protect domestic industries from foreign competition by making imported goods more expensive. Import duties can vary based on the type of product being imported, and they are typically calculated as a percentage of the value of the goods or as a specific amount per unit.

The other options do not accurately define import duty. A fee paid for domestically sold goods pertains to sales tax or value-added tax, which is distinct from import duties. A charge on goods being exported relates to export duties, which are not applicable to imports. Lastly, a fee for shipping goods internationally is focused on logistics and transportation costs rather than the taxation of goods upon entering a country. Thus, the correct understanding of import duty aligns precisely with the definition provided in the correct choice.