中文：

自由贸易是指在国际贸易领域中，通过降低或取消关税、非关税壁垒等措施，促进全球贸易自由化的政策。自由贸易旨在促进各国之间的贸易往来，加强经济合作和全球化进程，以实现资源的最优配置和经济的共同繁荣。

自由贸易的理论基础源于比较优势理论。该理论认为，每个国家都有其独特的比较优势，通过自由贸易，每个国家都可以专注于生产自己具有比较优势的产品，并通过与其他国家的贸易交换来获取自己所需的其他产品。这种分工和交换可以使得全球资源得到更加合理的利用，提高全球生产效率，并使消费者能够享受到更加丰富、多样化的商品和服务。

然而，自由贸易的实施也面临着一些挑战和争议。一些人认为自由贸易会损害本国的就业机会和产业发展，因为他们可能无法与外国企业竞争。此外，一些人还担心自由贸易会加剧贫富差距，使得富裕国家与贫困国家之间的经济差距进一步拉大。

总的来说，自由贸易是一种基于比较优势理论、以促进全球贸易自由化为目标的政策。尽管存在一些争议和挑战，但自由贸易仍然是全球经济繁荣和发展的重要推动力量。

英文：

Free trade refers to a policy of promoting global trade liberalization through measures such as reducing or eliminating tariffs and non-tariff barriers in the field of international trade. The goal of free trade is to facilitate trade exchanges between countries, strengthen economic cooperation, and promote the globalization process in order to achieve optimal resource allocation and common prosperity of the economy.

The theoretical basis of free trade stems from the theory of comparative advantage. This theory argues that each country has its unique comparative advantage, and through free trade, each country can focus on producing the products in which it has a comparative advantage and exchange them with other countries for the products it needs. This division of labor and exchange allows global resources to be used more reasonably, improves global production efficiency, and enables consumers to enjoy a more rich and diverse range of goods and services.

However, the implementation of free trade also faces some challenges and controversies. Some people believe that free trade can damage a country's employment opportunities and industrial development because they may not be able to compete with foreign enterprises. In addition, some people are concerned that free trade will worsen the gap between the rich and the poor, making the economic gap between wealthy countries and poor countries even larger.

Overall, free trade is a policy based on the theory of comparative advantage and aims to promote global trade liberalization. Despite some controversies and challenges, free trade remains an important driving force for global economic prosperity and development.