Green peppercorns are the same unripe berries that come from the same vine as black peppercorns (piper nigrum). They are simply the same black peppercorns, only picked early and unripe. As a result, they are much milder than black or white peppercorns and have more of a vegetal and fresh flavor. They are often used fresh in Thai dishes or French dishes such as the French steak au poivre where the whole green peppercorns are in the sauce.