Alcohol proof is a measure of how much alcohol (ethanol) is contained in an alcoholic beverage. In the United States, alcoholic proof is defined as twice the percentage of abv. So, 100-proof whiskey contains 50% alcohol by volume; 86-proof whiskey contains 43% alcohol.
In beer, alcohol content is 3-12% abv, but it is most often 4-6%. Conventional wines will have 9-16% abv, with most being between 12.5-14.5%. Fortifiied wines, such as port, madeira, marsala, sherry, and vermouth, have 15.5-20% abv. (The wine is “fortified” by adding a distilled spirit, usually brandy, to it.)
Stronger drinks, such as liquors, are distilled after fermentation to increase their alcohol content. These range from 20-95% abv.
Now you know.