Maison is French for "house" or "building," and when used as a wine term, it mainly refers to wineries in the Champagne region.
Similar words include "chateau" in Bordeaux and "domaine" in Burgundy, which refer to wineries in the aforementioned regions that handle everything from grape growing to brewing, aging, and bottling.
On the other hand, the Champagne houses tend to be larger companies than those in Bordeaux and Burgundy, and they purchase a lot of grapes from farmers to ferment. These large-scale Champagne makers are also called Grand Maisons.
In Champagne, houses that use purchased grapes are called "Négociant-Mapulant (NM)," while houses that use grapes grown in their own vineyards and handle the production process are called "Récoltant-Manipulant (RM)," and the abbreviation for this is printed on the label.
