There could be three main reasons First, the non-availability of a certain product in your country while it is available in another country. For example, bananas were not available in Britain, in the UK, prior to 1633 because their climate was not suitable for growing bananas. So, they would want to trade to import bananas. The second reason could be the availability of a product or service in another country, at a cheaper price as compared to your own country. A good example of this would be the call centers in India. US companies have set up their call centers In India because it's cheaper for them to do so here as compared to the US.  The third reason could be the availability of a product or service of better quality in another country. That is why you would want to trade with them. So the advantages of trading are very clear  Consumers will have more choices and have access to cheaper goods  Every country will be able to specialize in its own indigenous areas and be able to build better products and this could benefit all the countries internationally. So economically it's good for every country.  In fact, trading is so beneficial that research indicated that for every 1% increase in the trade to GDP ratio, There is a 0.47% increase in the GDP to per capita ratio of that country. So, there is a clear-cut relation here- trading increases the GDP of a country But this is a very simplistic explanation and there are many other complexities in the real world.