Prosciutto is a type of Italian ham that has been cured for up to 2 years. By the time it is done curing, the ham, even though it hasn't been subjected to heat, is ready to eat as is.
In the United States, the type of prosciutto available is prosciutto crudo, as opposed to prosciutto cotto, which is a cooked variety.
To cure prosciutto, the meat is salted to draw out moisture and inhibit bacteria. It is pressed to remove blood then left to dry out in the air--thus, the term "air-cured."
Prosciutto, like cheese and wine, can be labeled with a Protected Designation of Origin, which guarantees the product comes from a particular place where it is made in a particular way. Prosciutto di Parma and San Daniele are common in the U.S.
Country ham is an American air-cured ham that is sometimes used in place of prosciutto, though it is not usually available as shaved slices the way the Italian product is.
Some dishes call for briefly cooking prosciutto, sometimes as a prelude to adding other ingredients. This is done to lend the flavor of prosciutto to the dish.
Prosciutto flavors vary according to where the prosciutto is from. All are salty, but the spices used during curing, the food given to the pigs and other factors affect the flavor.