The national income of a country represents the total economic output and is defined as the money value of all final goods and services produced within a specific period. This metric reflects the productive capacity and economic health of a nation, as it captures not only the volume of production but also the market dynamics that assign monetary value to this output. By focusing on final goods and services, the national income avoids double-counting that could occur if intermediate goods were included, thus providing a more accurate representation of the economy's performance, which is crucial for policy formulation and economic planning.