If you want to understand the wide world of blue cheese, start by getting to know these four classic, flavor-forward styles.

IF YOU SEE SOMETHING labelled simply “blue cheese,” don’t trust it. Just think: If someone handed you a sandwich filled with “meat,” or your glass were poured high with “alcohol,” you’d recognize you were in trouble. Anonymous blue cheese isn’t so different.

Blue cheeses are indeed one big family—with a few uniting traits and idiosyncrasies, just like yours—but Fourme d’Ambert is not Maytag is not Picon. All do share the namesake blue (or green or indigo) streaks running through the curd. This colorful web is actually edible mold (typically Penicillium roqueforti), and it’s what gives the cheeses their signature mineral funk.

The world over, the myths surrounding blue cheeses’ origins have a similar ring. A careless shepherd forgets his fresh cheese sandwich in a cave. Or a distracted cheesemaker leaves in a hurry to meet his lover, neglecting an uncovered vat for too long. All come back to find their folly transformed into something surprising and delicious.

Blue cheeses can be anything from buttery and soft in character to stinging, hard-edged and metallic.

These days the process usually goes like this: Curds are gathered up into a large wheel, exposed to mold in a controlled fashion, and left to age in a cave or similarly dank and drafty environment for anywhere from a few weeks to a few years. Most are poked with needles to circulate oxygen through the cheese, which feeds and encourages more blue mold snaking through the curd.

As long as humans have tended cows, goats or sheep, cheese has been a natural byproduct, a way of preserving milk in its “leap toward immortality,” as the essayist Clifton Fadiman once said. But a blue cheese speaks particularly clearly of its home: the flock and its feed, the local caves and the invisible molds hanging in the air. Its terroir makes it what it is.

Because of this, blues can be anything from buttery and soft to stinging, hard-edged and metallic. So at the cheese counter, how do you know what you’re getting into? Start with a refresher course in four classic, widely available styles: French Roquefort, English Stilton, Italian Gorgonzola and Spanish Cabrales. All are protected to varying degrees by EU law, so they are still crafted in much the same way they have been for centuries. American blues, too, come in dozens of delicious styles made everywhere from Oregon to Vermont, but a better understanding of these begins with a survey of their old-world forebears.

According to Steven Jenkins, cheesemonger at New York’s Fairway Markets and author of the iconic “Cheese Primer,” “The Big Four are of unassailable quality, worthy of every accolade and certa