GDP

Gross Domestic Product is a measure of a country's overall economic output. It is the market value of all final goods and services made within the borders of a country in a year. It is often positively correlated with the standard of living,though its use as a stand-in for measuring the standard of living has come under increasing criticism and many countries are actively exploring alternative measures to GDP for that purpose

GDP can be determined in three ways, all of which should in principle give the same result. They are the product (or output) approach, the income approach, and the expenditure approach.
The Expediture Approach:

GDP = private consumption + gross investment + government spending + (exports − imports),GDP=C+INV+G+(EX-i)