Looking like a strip steak with a fish head, the pancreas is about six inches long. Attached to the muscles and tissues near your back, the pancreas has two very different roles and specialized exocrine and endocrine parts to carry out these tasks. (Exocrine implies that it secretes and has actions locally; endocrine means that it most commonly secretes into the bloodstream.)
The exocrine role is performed by acini—grape-like bundles of cells that secrete pancreatic juice. When food hits the first part of your small intestine, these cells squeeze out juices to digest food so it can be absorbed in the small intestine. The pancreatic juice also neutralizes the strong acids from the stomach so they don't damage the intestine downstream. This also explains the dangers of pancreatitis, which is often caused by a blockage of the pancreatic duct. This forces these powerful chemicals to spill over and literally digest the pancreas itself.
The pancreas is also important because pancreatic enzymes play very specific roles in how protein, fat and carbohydrates are broken down chemically so they can be used elsewhere in the body. The good news is that although the levels of digestive juice decline as you age, you usually die with your pancreas having considerable kick to do its digestive job, so you really never have to take supplemental digestive enzymes unless you get a pancreatic disease or are born without them.
Think of your pancreas as your body's internal juicer.