Prosciutto is the Italian word for ham. In English, the term is almost always used for an aged, dry-cured, spiced Italian ham that is usually sliced thin and served uncooked; this is called prosciutto crudo 'raw ham' in Italian and distinguished from prosciutto cotto 'cooked ham'.
The word prosciutto derives from the Latin perexsuctum, which gave way to the modern Italian word prosciugare which means "to thoroughly dry" (literally, "having been very sucked out").
In Italian, "prosciutto" refers to the pork cut, not to its specific preparation. Italian speakers therefore make a distinction between prosciutto cotto (literally, "cooked ham"), which is similar to what English speakers would call "ham", and prosciutto crudo ("raw ham"), the dry-cured ham which English speakers refer to as simply "prosciutto" or "Parma ham".
The most renowned and expensive legs of "prosciutto" come from central and northern Italy (Tuscany and Emilia in particular), such as Prosciutto di Parma, and those of Friuli-Venezia Giulia, such as Prosciutto di San Daniele.
San Daniele is the best variety (not brand) of prosciutto. Very pink and slightly sweet. This is just my opinion of course, but that is at least as good as the truth, if not better.