There are different measures of inequality, each of which summarizes, in one number, the dispersion in the distribution. The Gini coefficient and the MLD are two such measures.
The Gini coefficient has perhaps become the ‘default’ measure of inequality, ranging from zero to one. When it equals zero, everybody earns the same income: perfect equality. A Gini of one means that all resources go to one person: maximal inequality. In practice, societies range somewhere between these extremes.
MLD stands for Mean Logarithmic Deviation. It is another way to measure inequality, which is more sensitive to gaps in the bottom of the distribution. The minimum value for MLD is also zero, but it doesn’t have a maximum.