Prime grade beef is the absolute highest quality beef available, graded by the USDA. This is a very rare, and thus very expensive, only averaging about 3% of all carcasses. The beef has very minor, but a good amount of fat running through the meat, resulting in an amazingly juicy and tender cooked piece of meat.
Porterhouse steaks consist of a T-shaped bone with meat on each side, the larger side containing meat from the strip loin, whereas the smaller side contains the tenderloin. They are not to be confused with T-bone steaks, since porterhouse steaks are taken from the back end of the short loin, resulting in larger pieces of tenderloin, versus the T-bone steak, taken from the front end of the short loin and having less portion of tenderloin.