Monterey jack, sometimes shortened to jack, is a californian white, semi-hard cheese made using cow's milk. it is noted for its mild flavor and slight sweetness. it has been called "an american original" and "as a vestige of spanish rule in the early nineteenth century, derives from a franciscan monastic style of farmer's cheese."in addition to being eaten by itself, it is frequently marbled with colby to produce colby-jack, or with yellow cheddar to produce cheddar-jack. pepper jack is a version flavored with chili peppers and herbs. dry jack is a harder cheese with a longer aging time.

Source: Wikipedia