Champagne is an Appellation d'Origine Contrôlée (AOC), guaranteeing know-how and a strict geographical origin. Here are a few essential labels:
Grand Cru and Premier Cru: these designate the most prestigious vineyards.
RM (Récoltant-Manipulant): producers who grow their own grapes and vinify their own champagne.
NM (Négociant-Manipulant): a company that buys grapes to produce its own champagne.
Another element to consider is the mention "Blanc de Blancs" for a champagne made exclusively from Chardonnay, offering incomparable freshness, or "Blanc de Noirs" when produced from Pinot Noir and/or Pinot Meunier, giving more powerful aromas.