Pork chops are any meat cut from the loin portion of a pig. The loin is basically the back of a pig. The loin is divided into four categories, the first of which is located towards the head of the pig on its shoulder, and is called the shoulder chop. The biggest portion of the loin, located in the middle of the back, is commonly called the "center cut" and consists of both the rib and loin chops. Towards the butt of the pig is the sirloin chop.
Before the civil war, pork chops were the most popular meat in the United States. Back then, the richer you were, the higher up on the pig you ate, so the pork chop was an expensive cut. From the 1860's to the early 1960's, american pigs were called lard hogs, because they were about 60% fatter than today's hog. The pigs of today came from a cross breeding of lard hogs and the leaner bacon hogs, and a special diet to promote leaner muscle growth.
Because the shoulder chop contains a lot of different muscles and connective tissue, it is best cooked using a slow cook method, such as braising. Rib chops are best suited for fast, dry cooking, so if you're lookin' to grill, this is the cut for you. Because the pig has naturally dry meat, it is common to let all cuts sit in a brine. This helps them retain a lot of their moisture when cooking. A common favorite preparation for many involves the pork chop being topped, stuffed, or rolled with fruits and onions.