Digestif is the French term for booze that you drink after dinner, supposedly as an aid to digestion. Conversely, apéritif is the French term for booze you drink before dinner, in order to stimulate your appetite.
As to what is considered an apéritif, CHOW’s Juice columnist Jordan Mackay says that the term is used to refer to light predinner wine or cocktails, as well as the category of fortified, herb-infused wines and diluted spirits that includes stuff like vermouth. If you want to venture beyond a glass of wine before dinner, some good, easy apéritifs include the Aperol Spritz, Lillet over ice with a lemon twist, and the Americano.
In a study published in 2007, researchers at the Department of Psychology at Glasgow Caledonian University in the U.K. asked if drinking a glass of wine 20 minutes before dinner had any effect on appetite. While the serving size was on the large side (half a bottle!), the results suggest that consuming alcohol before a meal led people to eat more. (And anyone who’s ever been caught stuffing his face with greasy hot wings at a bar will know that drinking seems to stimulate the appetite.)
Digestifs have a broad definition, but they tend to be stronger than their appetite-whetting counterparts. They can be anything from straight Cognac or brandy to strong herb- or citrus-infused spirits like limoncello (see video below), and they are intended to be sipped slowly after a meal. You can make your own infused digestifs easily at home, in flavors like orange, fennel, and basil.
Do digestifs really help with digestion? Many medical studies (such as this, this, and this) show that alcohol, particularly consumed in large amounts, is not so hot for your digestive system, and can cause heartburn and diarrhea. So enjoy your digestif for what it is: a delicious glass of Cognac, not a curative.