The Concept of Comparative Advantage is explained below:

To illustrate the concept of the comparative advantage, we take the instance of two equi-sized equi-endowment countries, which are US and UK. US produces 40 and 60 units of cotton and food p.a. respectively (using all available resources), while the UK produces 30 and 20 units of cotton and food p.a. respectively (using all the available resources). Clearly, the US has complete advantage in the production of both cotton and food. By absolute advantage it is meant that the US is more efficient at producing food and cotton both than the UK. But, upon computing the opportunity costs of producing cotton and food in the either country, is revealed that the opportunity cost of producing one unit of the cotton in the US is 1.5 units of food, while the opportunity cost of producing one unit of food in the US is 0.67 units of cotton. Similarly the opportunity cost of producing one unit of the cotton in the UK is 0.67 units of food, whereas the opportunity cost of producing one unit of food in the UK is 1.5 units of cotton. Hence, the US has a lower opportunity cost (comparative advantage) in production of food while the UK has a lower opportunity cost (comparative advantage) in production of cotton. By specializing in the goods/commodities they have comparative advantage in and then trading between them, both the countries can improve their consumption possibilities beyond those implied by autarky (that is a situation of no trade where the PPF and CPF are the same).