Foie gras is a specialty food product made of the liver of a duck or goose. According to French law, foie gras is defined as the liver of a duck or goose fattened by gavage (force-feeding). In Spain and other countries, it is occasionally produced using natural feeding. Ducks are force-fed twice a day for 12.5 days and geese three times a day for around 17 days. Ducks are typically slaughtered at 100 days and geese at 112 days. Foie gras is a popular and well-known delicacy in French cuisine. Its flavor is described as rich, buttery, and delicate, unlike that of an ordinary duck or goose liver. Foie gras is sold whole or is prepared into mousse, parfait, or pâté, and may also be served as an accompaniment to another food item, such as steak. French law states that "Foie gras belongs to the protected cultural and gastronomical heritage of France."

Source: Wikipedia