The chaotic nature of the Republic of the Congo has produced an even more unsettling economy. The economy that has developed is an interesting mix between the primal mixture of village handicrafts and agriculture and the more modern developments of industry largely based on oil (petroleum) extraction, all of which stem from a government characterized by widespread hatred, budget problems, and severe overstaffing. Recently the boom in demand for petroleum has become substantially the countries most profitable revenue source since the late 1980s. The exponential growing oil revenue stream enabled the government to finance a large scale development project, one that was able to produce a 5% increase in GDP of the Congo per year. This was a substantial increase, but it also came with government shortages in revenues as they mortgaged a good portion of the earnings. Recently, new oil fields were discovered under various oil fields, which has lead to the Congo's oil production being projected to continue to grow significantly in the next few years.
The rest of the Congo's economy is centered around the sale of the other natural resources such as the countries abundant rain forests serving as a source of timber. The forest industry was prevalent and prosperous until recent years where high transport costs, high wages, and poor productivity have lead to the decline of the timber industry.
Sources:
http://en.wikipedia.org/wiki/Economy_of_the_Republic_of_the_Congo
http://www.africaneconomicoutlook.org/en/countries/central-africa/congo-republic/