The gallbladder is an accessory organ in aiding digestion. It acts as a storage unit for bile, which is needed for digestion of lipids (fats). The bile is made in the liver and passed to the gallbladder where it is stored for future use. This is why people can live after they get there gallbladder removed. The bile will still get made and can still be secreted down to the small intestines, there just won't be a storage of bile.