Fermentation is a gradual chemical change in which, in the case of alcohol,
sugar or starch is broken down into ethanol and carbon dioxide.C6H12O6
= C2H5OH + 2CO2 (Gay-Lussac 1815)
In natural fermentation, the ethanol content is limited to a maximum of about 14%. Distillation separates out the ethanol so that it becomes more concentrated.
More information: http://web.ukonline.co.uk/webwise/spinneret/microbes/fungi.htm
In everyday usage, when we say "alcohol," we mean ethanol. The ethanol found in beer, wine and spirits. Methanol is found in antifreeze, household cleaning solvents and other "non- edible" products. This type of alcohol is extremely poisonous and can cause sickness, blindness and death. The isopropyl alcohol used in rubbing alcohol is also dangerous.