Comparative Advantage is an economic idea that explains why individuals, businesses, or countries can benefit from specializing in producing goods or services where they have a lower opportunity cost. Opportunity cost is what you give up to produce something else.
For example, if Country A is really good at making cars and Country B is really good at growing coffee, even if Country A could make coffee, it might be better for them to focus on cars and trade with Country B for coffee. This way, both countries end up with more cars and more coffee overall.