Mercantilism is the economic philosophy that basically states that a nation must export more than it imports in order to compete with everyone else. It was really the first economic theory linked to global trade, and it shaped the entire Age of Exploration. The whole investment/financial colonization scheme, such as the Virginia Company of London, was designed on the principle that a nation, such as England, could get its resources from a colony, and not need to import it from France and Spain.
This is why the Brits hated it when Americans tried to be self-reliant, such as building products instead of send raw materials home to be manufactured in British factories. They also were unimpressed when we would trade with their rival nations, leading to an undermining of the whole mercantile principle, and outright smuggling.
As you can see, mercantilism is a surefire way to create world wars between the major empires. Its also a great way to create conflict between a successful colony and its master.
Capitalism basically states, everyone specialize in producing and exporting whatever products and materials that you can make very well, cheaply, and efficiently. It rejects the zero sum game of control over resources, and Adam Smith viewed it as a means to create friendship and peaceable commerce between nations rather than endless imperial wars.