Gaillac method (Ancestral): Gaillac wines gained reputation with this very old winemaking method at the beginning of the 20th century. It would predate the discovery of Dom Pérignon, who revolutionized Champagne production between 1668 and 1695. In fact, the Gaillac method was found much earlier in around 1591. The winemaking method is natural without adding sugar for bubbles or liqueur d'expedition for some form of sweetness. The Gaillac method only makes use of the sugar contained in the grape throughout the process and ensures the first fermentation, the bubbles and the residual sugar of the wine. 
 
Source: dico-du-vin.com
 
 
The traditional method is a sparkling wine production method where a second fermentation takes place in bottles of still wine after the addition of liqueur de tirage. The traditional method of sparkling wine production is identical to the champagne winemaking method. Community rules prohibit the use of the term "méthode champenoise" (or "champagne method") in the labelling of sparkling wines other than Champagne since 3 August 1994. 
 
Source: vinsvignesvignerons.com