why steak differentiate with tenderloin and sirloin

I'm not really clear on the difference except they come from different parts of the steer. A steak from the rear is more tender than one from the flank because the flank has more muscle. One way to cook a cheap and less tender cut of meat is to bake it in tin foil. season it then put some Worcestershire sauce on it--or any other liquid flavoring--some onions and perhaps a potato and some carrots. Seal it up and put it on a baking sheet, bake at 400 degrees for 45 minutes then turn it down to 300 for another 45 minutes. No matter how tough the meat is, it will come out tender and delicious.