1.   M/L is the mass-to-light ratio, measured in units of  solar mass/ solar luminosity (usually in the blue band). The mass is usually the total gravitating mass, including any dark matter.

Since (Bothun 4.1) the luminosity of Main Sequence stars rises approximately as mass to the 3.5, the M/L ratio goes as mass to the -2.5. This gives M/L~55 for a 0.2 solar mass star.