The pancreas is not in the same location in every person. In people with a condition called situs inversus totalis, the pancreas and all other organs are reversed.
In most people, the pancreas is a six inch long organ found behind the stomach, with its head on the right side of the abdomen. In those with situs inversus totalis, the head of the pancreas is on the left side of the abdomen.
Wherever the pancreas is, it is a gland that produces insulin, which is crucial for the body's ability to use glucose, or blood sugar. When insulin isn't produced or can't be used, it leads to diabetes.