GDP (gross domestic product) is referred to as the gross domestic product of a country - amount of goods and services within one country, and per capita GDP is about GDP per person. Therefore, a total amount of GDP (this information is usually found in the bureau of the census report) should be divided by a total number of population. For example, if GDP is 100,000 and a total population is 100, per capita is 1000 (100,000/1000).
And, information about per capita GDP is useful when people compare one country with another because it presents each country's performance on gross domestic product.