These drinks are made by a process called distillation. Distillation is the process of heating a liquid and turning it into a vapor, then turning the vapor back into a liquid. Doing this creates a much higher concentration of alcohol. Fermentation will only produce about 15 percent alcohol. Distilling a fermented liquid can result in a drink of as much as 50 percent alcohol.
Proof is twice the alcohol content.
Gin, Bourbon, Vodka, Rum and Liqueurs.