Gross Domestic Product, or GDP, is a measure of the total economic output of a country. It represents the total value of all goods and services produced over a specific time period, usually a year or a quarter. GDP is used to gauge the health of a country's economy and to compare economic performance between different nations. There are three main ways to calculate GDP: the production approach, which adds up the value of all goods and services; the income approach, which sums up all incomes earned; and the expenditure approach, which totals all spending on goods and services. Understanding GDP helps policymakers and economists make informed decisions.