Spirits distillation is the process of heating a fermented liquid, evaporating off the alcohol as vapor, and then condensing it back into liquid form.

Spirits can be made from any organic substance that can be fermented to create alcohol. Most alcoholic beverages are made by fermenting fruit or grain-based solutions. A still extracts alcohol from a fermented liquid by boiling it and then condensing the alcohol vapors, which evaporate from the boiling liquid at a lower temperature than water.

Spirits are measured by alcohol content. Different scales are used in different countries. Most countries use alcohol by volume (ABV), also known as the Gay-Lussac system, which expresses alcohol content as a percentage of the total liquid volume of the beverage. A 40% ABV spirit contains 40% alcohol. In the United States, the proof scale of measurement is used, with the proof of a spirit being double the ABV. Thus a 40% ABV spirit is 80 proof.

Generally speaking, spirits are classified by the fermented material they are distilled from. Whiskies, Vodka, Gin and most types of Schnapps are made by distilling a kind of beer made from grain. Brandy is made from fermented grape juice, and Fruit Brandy is made from other fruits. Rum and Cane Spirits derive from fermented sugar cane juice or molasses. Tequila and Mezcal come from the fermented pulp of the agave plant. Fortified wines are hybrid beverages in that they are a blend of fermented wine and distilled spirits (usually Brandy).