Mercantilism was an economic policy developed in the 18th century that was based on maximizing a nation's exports in order to gain an economic advantage over its foreign counterparts.
On the other hand, Capitalism is an economic doctrine that is based on a free market in which private entities can accumulate wealth as a product of their economic activities.
The system is similar in the way that both promoted economic supremacy of the Western Powers over other nations, particularly the newly formed nations which have just acquired their independence such as the countries in Latin America and Africa.