It's used to soften stones pre-flush. "Sweetish" bitters is a mixture of herbs taken before meals to stimulate bile production, more of a digestive aid. :)
Edited:
I just re-read Lakelight's post and saw that she was, indeed, refering to Chinese bitters. The main ingredient in both the Sweetish Bitters and the Chinese bitters is gentian, an extremely bitter herb. It stimulates bile production by it's bitterness. Sweetish bitters is taken before meals, the chinese bitters is taken 1x a day. I am ASSUMING that the Chinese bitters is also taken to increase bile production by the fact that it also contains gentian. I don't know anything about the other ingredient in the Chinese bitters...time for some research! I can tell you, from personal experience that the Sweetish bitters (Gaia herbs) is also bitter, but they add other herbs for flavor. :)