The gross domestic product (GDP) or gross domestic income (GDI) is one of the measures of national income and output for a given country's economy. GDP is defined as the total market value of all final goods and services produced within the country in a given period of time (usually a calendar year). It is also considered the sum of a value added at every stage of production (the intermediate stages) of all final goods and services produced within a country in a given period of time, and it is given a money value.
The most common approach to measuring and understanding GDP is the expenditure method:

GDP = consumption + gross investment + government spending + (exports − imports), or, GDP = C + I + G + (X-M).