Per capita income is the mean income calculated for a group, population, country or larger area that expresses the hypothetical income for every man, woman and child listed in a census of the group, population, country or area. It is hypothetical because, since per capita income is a mean figure, it may or may not not represent the actual income of any single individual in the census group. It is important to note that while every child, including those too young to earn income, is represented in per capita income (every one of even the youngest children is attributed an income), not every child adds income to the mean calculation. Per capita income is calculated by dividing the total income of a census group by the total number of individuals in that group (be it group, population, country or area).
[Per capita income] is derived by dividing the total income of all people ... in a geographic area by the total population in that area. (U.S. Census Bureau)
As an example of per capita income of an African nation, the per capita income of Botswana in 2012 was $16,800, PPP.
If you ever need more stats like this, use the CIA.gov link below. Pick a country from the drop down and click the "Economy" tab.