Like Parmigiano-Reggiano, Champagne, Burgundy, or ProsciuttodiParma this means that it can only be legally made in a certain place under specific rules with specific labeling requirements.
While ProsciuttodiParma and its close Italian relative, Prosciutto San Daniele, are both excellent and both readily available in this country, lower quality domestic imitations of both are even more readily available.