On the pig/hog, there are basically two types of ribs.. the baby backs and the spare ribs.
The baby backs have less fat and are a little more aesthetically pleasing (allegedly) than the fattier, more oddly shaped spare ribs. For this reason, it is common to trim them up. In doing so, a lot of the less desirable parts are removed and they end up looking more like a baby back.
“Here's how to do that”
Cut off that bone that juts out on one side(diagonal piece at lower left of slab).. it's mostly cartilage so it can be cut with a sharp knife pretty easily. A cleaver will work if your aim is pretty good
Next cut off the brisket bone which runs along the same side as the piece you just removed. If you feel carefully along the ribs, you can feel a joint separating the brisket bone from the rack of ribs. This is where you make your cut.
To finish the trim work, simply cut off the extra flap of meat on the small end of the ribs (right side of slab below) and you are finished.
Place all of the extra pieces in a pan and set them aside. They can be smoked right along with the other ribs or you can freeze them and smoke them later. Once cooked/smoked they can be stored and added to beans, soups, stews, etc. for great flavor.