GDP of a country is defined as the total market value of all final goods and services produced within a country in a given period of time (usually a calendar year). It is also considered the sum of 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.
The most common approach to measuring and understanding GDP is the expenditure method: GDP = consumption + investment + (government spending) + (exports – imports), or, GDP = C + I + G + (X-M)