Meters Above Sea Level — the elevation at which coffee is grown. Higher altitude = cooler temperatures = slower cherry maturation = denser beans = more complex flavor potential. Specialty coffees typically grow above 1,000 MASL; the best often above 1,800 MASL.
Nariño grows coffee above 2,000 MASL. Brazil grows most of its coffee below 1,200 MASL. Both can be specialty grade, but the flavor profiles differ dramatically.