IN MODERN TIMES
we mostly use them for delivering flavor & color in cocktails, but their history is as a folk remedy... 

Called an amaro in Italian or an amer in French, bitter liqueurs have been made & consumed all over the world for centuries due to their unique effects on the diet.

Certain bitter liqueurs function as aperitifs when taken as a long drink or mixed with wines and have been known to stimulate the appetite before a meal. Taken on their own or mixed with spirits, bitters are believed by some to function as digestifs, intended to settle the stomach after eating.