Not a true peppercorn, but rather the dried berry/seed of a deciduous prickly ash tree.
With its unique aroma and flavor that is not hot or pungent like black or white pepper, or chili peppers, but has slight lemony overtones and creates a tingly numbness in the mouth that sets the stage for these hot spices. Recipes often suggest lightly toasting and then crushing the tiny seedpods before adding them to food. It is generally added at the last moment. Star anise and ginger are often used with it and it figures prominently in spicy Szechuan cuisine. Not a true peppercorn, but rather the dried berry/seed of a deciduous prickly ash tree.