Pancetta and procuitto are both pork products that come from italy.
Pancetta is pork belly (or bacon) that is very similar to bacon in the US, but is is rolled into a large log rather than sliced into strips. You can find it in thin rounds or chunks. Cook it the same you would bacon.
Procuitto is more similar to ham. It comes from the hind leg portion of a pig and it is cured and dried. Procuitto is dried for a very long time and is best eaten as is without any cooking neccisary. Pancetta on the other hand is best served cooked.
Both are ham products but from different parts of the animal. Pancetta is similar to American Bacon while prosciutto is more like Ham, more specifically Country Ham.