Bacon and pancetta have the
most in common. They are both typically made from pork belly and
both are cured for a certain length of time. Both are also
considered raw and need to be cooked before eating.
The process for making the two is slightly different. Pancetta is
simply cured with salt, but spices and other aromatics are often
added to infuse the pancetta with other flavors. Pancetta is
sometimes sold sliced paper thin, or cubed. The thin slices can be
wrapped around vegetables or meat before cooking. The pancetta cubes
are often used like bacon, sautéed with onions or garlic to form the
base of a soup, pasta, or risotto.
Bacon is also cured, like pancetta, but the meat is smoked after it
has been cured. This is usually a cold-smoking process, meaning that
the bacon isn't actually heated or cooked during smoking and remains
raw. Smoking can be done with a wide range of woods, from apple to
maple, which each give their own distinctive flavors to the meat.
So pancetta is cured and unsmoked, while bacon is cured and smoked,
but both need to be cooked before being eaten. They can be used
interchangeably in dishes.
Prosciutto is very different from either bacon or pancetta.
Prosciutto is made from the hind leg of a pig (ie, the ham), and
outside Italy, calling it prosciutto indicates a ham that has been
cured.
The quality of prosciutto depends on the curing process. The outside
of the ham is usually rubbed with just salt and sometimes a mix of
spices. This draws out moisture and concentrates the flavor while
the ham slowly air-dries. This process can take from a few months to
a several years depending on the desired result. Once cured,
prosciutto is usually thinly sliced and eaten as is, uncooked.
Sometimes prosciutto gets lightly cooked as a finishing touch to a
pasta sauce or other dish, but this is more to bring out the aroma
and merge flavors.