I have been wondering what a prime rib really is. So here is what I found on the net.
#1 Prime rib is a classic roast beef preparation made from the beef rib primal cut, usually roasted with the bone in and served with its natural juices (au jus).
Restaurants that serve prime rib are required to use beef that has been graded prime by the USDA. Otherwise they have to call it a standing rib roast, which is decidedly less exciting sounding, or a rib-eye roast for the boneless version.
#2 A standing rib roast, also known as prime rib, is a cut of beef from the primal rib, one of the nine primal cuts of beef. While the entire rib section comprises ribs six through 12, a standing rib roast may contain anywhere from two to seven ribs.
It is most often roasted "standing" on the rib bones so that the meat does not touch the pan. An alternative cut removes the top end of the ribs for easier carving.
Rib eye steaks are cut from a standing rib, boned with most of the fat and lesser muscles removed.
While historically known as a “prime rib”, the USDA does not require the cut "to be derived from USDA Prime grade beef"
