Pancetta is made from pork belly that's seasoned with salt and various spices, then rolled and cured, often with pepper or other flavorings. It's typically eaten cooked.
Prosciutto, on the other hand, is made from a pig's hind leg. The meat is aged for anywhere from nine months to two years, giving it a delicate, melt-in-your-mouth texture.
Slices of prosciutto have a small margin of fat, which provides a contrast to the saltiness of the cured meat. Prosciutto is much higher in lean muscle than pancetta.