In vertebrates the gallbladder (cholecyst, gall bladder, biliary vesicle) is a small organ that aids mainly in fat digestion and concentrates bile produced by the liver. In humans, the loss of the gallbladder is, in most cases, easily tolerated. The surgical removal of the gallbladder is called a cholecystectomy.
Read more about Gallbladder: Human Anatomy, Microscopic Anatomy, Function, In Other Animals