The best way to differentiate between these is to look at the animal and see where they come from:
This is a whole pig with the backbone split down the center, but not separated.
Let's split it:
Now, let's draw cut lines to separate out the parts'n'pieces:
and label them:
First, let's take the Pork Belly Spare Ribs: these also have the pork belly attached, so we have to separate them into:
and Pork Spareribs:(front and back views):
Now, from the whole sparerib comes the St. Louis Style sparerib:
where the Rib Tips are separated from the ribs, and the
skirt is removed from the rack along with the membrane:
The Finished St. Louis Style Ribs:
Then, there is the Carolina Sparerib:
with only the brisket section removed, giving easier carving into individual ribs.
Now, above the sparerib/belly section is the Loin:
If you bone out the loin, you end up with a boneless pork loin:
with the bones separated.
Cut the rib bones from the back bone:
And that is where baby back spareribs come from!
How much meat is left on from the loin is the choice of the meat cutter.