It's what happens when the sugars in fruits or grains are converted into alcohol molecules. Early humans may not have understood the process at first, but they stayed with it and their descendants gradually came to learn that the lowly yeast cell, which occurs naturally on the skins of grapes and other fruits, is the key to the fermentation process. And it's fermentation, we know, that puts the kick in liquor and the cheer in beer. The problem is that it also lights the fuse in booze. The fuse in booze that gets things confused is a chemical called ethanol , or ethyl alcohol .
Ethanol is just one type of alcohol, but it's the only one that can be safely consumed by humans.
Other forms include methyl and butyl alcohol , which are toxic poisons and used mostly in medical and industrial products, like rubbing alcohol and antifreeze. That doesn't mean that ethanol isn't poisonous. It's just less toxic than its chemical cousins. It can cause the same problems, even coma or death, at higher dosage levels. By the percentage of pure ethanol present.