The job of the pancreas is to produce digestive enzymes and secrete hormones used in the metabolic process, such as insulin and glucagon.
Pancreatitis is inflammation of the pancreas. When a cat’s pancreas becomes inflamed, it allows digestive enzymes to escape, causing damage to both the pancreas and the nearby liver.
According to Suite101.com:
“Feline pancreatitis may be acute or chronic and can vary from mild to severe. Cats affected by pancreatitis often are simply not "acting themselves", although more symptoms such as vomiting and abdominal pain may be seen in some cats. Potential complications (diabetes, hepatic lipidosis, DIC, etc) can occur with feline pancreatitis and may make the disease even more life-threatening.”