The concept here is that if a country has a small population, then the per capita income would be large. by dividing the total income by the total population giving you the per capita income.
GDP, or gross domestic product, is how many goods and services a country or realm produces over an interval, usually a year.
the per capita part, means, the average per person, so you grab the GDP, say 5 trillion, and divide it evenly among all inhabitants, so a per-capita figure is really just GDP/population.
now, you can have a population like Germany with 80 million with a GDP of say hmmm 8000 million for simplification, the per-capita is then 8000/80 or $100 per person.
now, you could have another population like say Japan, and let's just say is less people... hmmm 20 million, with a GDP of say 4000 million.
then the per-capita in that example for Japan will be 4000/20, which is $200 per-capita, notice, the Japan's example has a higher per-capita, though the GDP is smaller to the example of Germany, that's because the Japanese population is also smaller.
sidenote: per-capita figures are often very misleading, since economies do not grow that linearly.
