Gross domestic product (GDP) ?

The market value of all final goods and services produced within nations geographic borders during a period of time.

The components of the GDP are Consumption, Investment, Government Purchases and Net Exports (Exports-Imports) .Stated as the following formula,
Y=C+I+G+NX or Y=C+I+G+(X-M)

Nominal GDP
The value of all final goods based on the prices during the time period of production.
Real GDP
The value of all final goods and services produced during a given time based on the prices of a selected reference year.