Ricardo's illustration of the Comparative Cost Theory, using a two country two-commodity model, shows that trade between nations am be profitable even if one of the two nations can produce both the commodities more efficiently than the other nation provided that it can produce one of these commodities with comparatively greater efficiency than the other commodity. The law of comparative advantage indicates that a country should specialise in the production of those goods in which it is more efficient and leave the production of the other commodity to the other country. The two nations will then have more of both goods by engaging in trade. ((i hope this helped if not i didnt understand ur question properly))
The theory of comparative advantage can be defined as the capability of a person or a country to manufacture an exacting good or service at a lower marginal and opportunity cost over another. Get some more information on http://en.wikipedia.org/wiki/Comparative_advantage.