Gini Coefficient is a measure of inequality in the distribution of income and can be shown as the area between the Lorenz curve and the diagonal divided by the total area beneath the diagonal (half square). Therefore, it can only yield any number between 0 and 1

Gross domestic product is the total value/output of final goods and services produced in an economy (in a given time period).

Gross National Income/Gross National Product (GNI/GDP) is made up of GDP plus net property income (current transfers) from abroad.