Gross Domestic Product, or GDP, refers to the total value of goods and services produced within a country's borders in a given time period. This includes the income earned by domestic residents from investments made abroad, but it also subtracts the income earned by foreigners in domestic markets. Essentially, it measures the overall economic activity of a country, taking into account both domestic and international factors. This is an important concept to understand in the field of finance, as it provides insight into a country's economic health and can impact investment decisions.