From Wikipedia: Amaro (Italian for "bitter") is an Italian herbal liqueur that is commonly consumed as an after-dinner digestif. It usually has a bitter-sweet flavour, sometimes syrupy, and has an alcohol content between 16% and 40%.
Similar liqueurs have traditionally been produced throughout Europe. There are local varieties in Germany (where they are called Kräuterlikör), in Hungary, the Netherlands, and France. But the term amaro is applied only to Italian products of this kind.
Amaro is typically produced by macerating herbs, roots, flowers, bark, and/or citrus peels in alcohol, either neutral spirits or wine, mixing the filtrate with sugar syrup, and allowing the mixture to age in casks or bottles.
Dozens of varieties are commercially produced, the most commonly available of which are Averna, Ramazzotti, Lucano, and Montenegro.
Many commercial bottlers trace their recipe or production to the 19th century. Recipes often originated in monasteries or pharmacies.
Amaro is typically drunk neat, sometimes with a citrus wedge. It may also be drunk on ice or with tonic water.
"A bitter by any other name: Campari is the best-known amaro stateside. But, because it is often served as an aperitif, some imbibers imbibers wonder if it belongs in the same category as after-dinner drinks like Fernet. We asked the experts. “Campari is a quintessential amaro,” proclaims Campari's own Dave Karraker."