The loin is a long piece of muscle running alongside the backbone and atop the ribs. It will be cut vertically, giving a oval/oblong cross-section somewhere around 4" diameter. That oval is solid muscle, although there may be some streaks of fat. There will usually be another strip of muscle above it, and a strip of fat along the top and one side (this was the pig's insulating back fat). Opposite the fat will be a rib bone, if it hasn't been removed.
The bone will not be split, but it will be cut short at some point. It is convex towards the fat, and usually has some of the fat running down along its length. If the rib is there, the steak (or "chop") will have a smaller oval of muscle below the loin, separated by fat, which would otherwise be served as part of the rib meat. As the cuts of the loin move backwards towards the leg, the tenderloin may begin to be incorporated, and the rib will disappear. The tenderloin is perhaps half the loin's size, and appears on the opposite side from the loin of a slice of the backbone, which has a rib-like sideways protrusion. This cut is the "porterhouse", also known as the "T-bone" if the steak were beef. It may also be called a "loin chop", as opposed to the "rib chop" from futher forward.
Rib/loin chop summary description: oval/oblong of solid meat with a strip of fat at one side, possibly an intact bone on the opposite side, curving towards the fat. Possibly two ovals of meat, one half the size and on the opposite side of a protrusion of split bone from the larger.