The common denominator for all types of beverage alcohol is fermentation, which is nothing more than the natural decomposition of organic materials containing carbohydrates and the conversion of the sugars in those carbohydrates into ethyl alcohol.
While fermentation is pretty much universal, historically, different cultures have used whatever source of carbohydrates was most common in their region. France, Spain and Italy were all wine producing countries where grapes were plentiful; as a result they developed a tradition of distilling wine or the left-overs from the wine making process and gave the world cognac, Armagnac, brandy de Jerez and Grappa. In the British Isles, grain was more plentiful and, as a result, the first whiskies were developed, while in Mexico fermenting the juice of the agave plant was the first step in the development of tequila.
Fermentation occurs in nature whenever the two necessary ingredients, carbohydrate and yeast, are combined in a liquid, and it was probably the accidental combination of the two, which resulted in the first beverage alcohol.
The liquid in which the fermentation takes place is sometimes called the mash. Fermentation stops when the sugars in the mash are depleted or when the alcohol level reaches about 14% and kills the yeast. In making beer and wine, fermentation is the most important part of the process.
For distilled spirits, however, that’s just the beginning. After fermentation, the liquid is then distilled one or more times, which reduces the original water content and greatly increases the alcohol level. Where beers on average have an alcohol content ranging from 2% to 8% and wines from 8% to 14%, distilled spirits are usually in the range of 35% to 50% alcohol, although individual products may be either higher or lower.
Distilled spirit labels often list proof in addition to alcohol content by volume. The proof level is always twice the alcohol content. (A bottle of 100 proof bourbon, for example, has an alcohol content of 50% by volume.)