There are basically two kinds of pork ribs. Those most commonly found in supermarkets are spareribs. The thicker and meatier ribs from the pork belly, they’re what’s leftover (or spare) after the bacon has been cut away. A full slab of spareribs consists of the front, or belly ends, of eleven ribs and the cartilage that connects the ribs to the breastbone. Many butchers remove the sternum portion and much of the connecting cartilage, leaving a narrower, better slab of ribs called a St. Louis cut. A slab of St. Louis spareribs weighs 2 to 3 pounds (smaller means more tender); each slab will feed two or three people. As when buying bacon, look for a good ratio of meat to fat; the fat will baste the meaty portion as the ribs cook. Spareribs come from the relatively tough but incredibly succulent belly portion of a hog, so they’re best cooked slowly and gently, which is why they’re often a first choice for slow-cooked barbecuing and braising.
Back ribs are leaner and smaller, from the top, back, or loin side of the hog. Since a good deal of pork loin is sold with the bone attached (i.e. pork chops and bone-in loin roasts), back ribs are a little less common and more expensive than spareribs. A slab of back ribs, sometimes called baby back ribs because of their rather diminutive size, includes eight ribs and weighs 1 to 2 pounds. The backbone is always removed from back ribs, making it a cinch to slice between the ribs to cut a slab into smaller portions. Most rib lovers figure one slab per person. Because back ribs come from the loin section of the hog, they’re more tender and lean but less flavorful than spareribs. Back ribs can be grilled or broiled as well as barbecued.
You may also see “country-style” ribs in the store. These aren’t ribs at all, but blade steaks or chops. Cut from the blade portion of the loin’s shoulder end, they often include part of the upper rib bones, though they may be boneless. They have a lot of connective tissue and fat, making them ideal for barbecue, not unlike real ribs.