Alcohol generally relates to those drinks that contain "alcohol" or ethanol. More specifically, alcohols are a group of organic chemicals that comprise carbon molecules ending in -OH, i.e. an oxygen and hydrogen molecule. Chemically, ethanol is C2H5OH, boils at 78oC (173oF) and freezes at a much lower temperature than water.
Ethanol is formed when the sugars in plants are fermented by yeasts. The main plants are grapes, potatoes, rice and fruit juices, all of which contain sufficient natural sugars to enable the yeasts to ferment the sugars. Ethanol is the active "drug" within most alcoholic drinks from beer through to wines, via vodka and sake.
Alcohol depresses. However, first it depresses those parts of the brain that cause depression and inhibition, so appearing to stimulate the psyche. Fairly soon thereafter, it results in impaired efficiency, slow reactions, recklessness, self-pity, bad temper, aggression and finally falling into the gutter. The alcohol starts to be absorbed into the bloodstream soon after a cup of alcohol has been sipped and has entered the small intestine. The absorption occurs quickly in an empty stomach, but more slowly when eating, especially when eating oily foods. So eating Meze (Middle East, tapas (Spain) or zakousky (Russia) do help slow down the uptake of alcohol. Unfortunately, it takes a lot longer for the human body to clear alcohol out of the blood than they are absorbed in the first place.
Alcohol is haram, so banned under Muslim dietary laws.
Alcohol in Cooking
Alcohol is synonomous with alcoholic drinks in cook's parlance. The important properties of alcohol for a cook are ethanol's ability to act as a preservative, so fruits can be preserved in alcohol, secondly its boiling point and thirdly the flavours from the drinks themselves.
Alcohol helps preserve food. Wine marinades help meat, fish and game keep for a short time in hot weather. Alcohol combined with sugar syrup makes elegant fruit conserves and stronger fruit liqueurs are used to preserve fruits.
At normal atmospheric pressure, ethanol boils at 78oC (173oF), while water boils at 100oC (212oF). Alcoholic drinks are all a mix of water and ethanol, so they boil between these two numbers. Therefore, stew or punches will slowly boil away the alcohol and more alcohol is lost the closer the cooking temperature gets closer to water's boiling point, especially as most cook their stews at a simmer around 95oC (203oF). This is, also, why you should not boil your mulled wine, or at least if you want the alcohol to help you through the trauma of a family Christmas.
Alcohol as a flavour is added to food either cooked or uncooked. Lower alcohol drinks, e.g. beers, ciders, and wines, tend to be added to sauces and cooked. This is partly for their water content but also for their flavours that are concentrated during the cooking process as the ethanol and water evaporates. Higher alcohol drinks - especially sweetened ones like marsala and sherry are poured over fruits or added to puddings without further cooking. There are exceptions - champagne is poured over peaches and anise-flavoured spirits are cooked in fish dishes. Often, ingredients are marinaded in alcohol before cooking which imparts distinctive, if subtle, flavours to the ingredients being prepared; wine, beer and cider are generally used for this.
Alcohols are used extensively in puddings as flavouring plus to give them a boozy uplift. Sherry, brandy and Marsala are added to creamy puddings - brose, cranachan, syllabub, tiramisu, trifle and zabaglione. Higher alcohol drinks are added to confectionery, combined with chocolate and sweets, in icings, cakes and fruit-based desserts.