Briefly describe several main theories of international trade.

The main theories of international trade mainly include theory of absolute advantage, mercantilism and infant industry protection trade theory.

Theory of absolute advantage: It refers to the absolute difference in the labor cost of producing a certain product between two countries, that is, the labor cost consumed by one country is absolutely lower than that of another country.

Mercantilism: refers to the national strength of a country based on its trade surplus, that is, the export volume is greater than the import volume, and the wealth it can obtain.

On infant industry protection trade: a new industry in a country may not stand up to foreign competition when it is still in the primary stage of the most moderate scale. If the industry can have a comparative advantage and contribute to the development of the national economy by adopting appropriate protection policies and improving its competitiveness in the future, transitional protection and support policies should be adopted. Mainly through the means of tariff protection.

Expansion: International trade refers to the exchange of goods and services between different countries or regions. International trade is the international transfer of goods and services. International trade is also called world trade. International trade consists of import trade and export trade, so it is sometimes called import and export trade.