What is the difference between GDP and GNP? 

Gross domestic product (GDP) is the value of the total final output formed inside a country, during a given year. GDP, like all measures of national income, is a flow (as opposed to stock) figure accruing over the period of one year. Gross national product (GNP) is the value, at current market prices, of all final goods and services formed during a year by the factors owned by the citizens of a country. Thus the income earned by Pakistani citizens working in the US would be contained in Pakistan's GNP but excluded from Pakistan's GDP. Conversely, the income earned by a US citizen (individual or corporate) in Pakistan would be included in Pakistan's GDP but excluded from Pakistan's GNP. Generally, GNP = GDP + net factor income from abroad.