Spare ribs are primarily most of the rib cage of a hog including the breast bone..With the breast bone (brisket) removed they become St Louis Cut Spare Ribs...Sometimes you will see (or mostly hear) of Kansas City Cut Spare Ribs... Where in addition to the removal of the breast bone the inside flap of meat ( remainder of the diaphragm ) is removed/trimmed off.. Both the St Louis, and the KC cuts have the small end trimmed off to "square up" the slab.~~ At the end of the day the difference is mostly about intrastate rivalry baloney!.
Country Style Ribs ~~ The North American Meat Processors Association says that country style ribs "shall be prepared from the blade end of a bone-in pork loin, and shall include not less the three ribs, and no more than six...plus some additional technical cutting.... They don't seem to be as fashionable as they once were...The "trendy" loin back ribs have the public's favor right now...and loin backs are just country style with loin meat removed...Wonder why anyone would choose loin back over country style??
I suppose they would rather have the trendy Hoity Toity, Artsy Fartsy "baby back" ribs... Even when 99% if them are not true 'baby backs" anyway.
Also, you will see another "Country Style Rib" in your grocers meat case. These are cut from the shoulder...specifically the butt portion....Obviously they are not "ribs" at all...they are just pork butt sliced/cut into strips...Once long ago in my area these "ribs" were labeled as "Western Style Ribs" to differentiate from true "Country Style"....I've not seen them labeled that way in years...So when your retailer advertises "Country Style Ribs...Are they true Country Style (from the blade end of the loin...or are they cut from the shoulder/butt?? Truth in labeling law says that somewhere on the package it must say what part of the hog the meat came from...I often see in bold print.. Country Style Ribs
...in small print over in a corner...Pork shoulder..... .In my area those cut from the shoulder dominate the store's displays and advertising....True Country Style are few and far between, but I do find them occasionally in Kroger stores...Most of the time I buy them from a small local processor. HTH