The tenderloin is a cut of beef, bison (also known as buffalo) or pork that comes from the short loin, the section between the ribs and the sirloin. It is specifically the part just under the spine, in an area used for posture rather than movement. According to Cook's Illustrated, it is the most tender cut of meat.
According to the Cook's Thesaurus, filet mignon comes from the narrow end of the beef or bison tenderloin. Moving away from the filet mignon end, the French call the resulting steaks tournedos, filet steak, chateaubriand and bifteck. Pork tenderloins are cooked whole or sliced into individual scallops or medallions. All tenderloins are lower in fat, slightly less flavorful but very tender and more expensive than other cuts of meat.
Whole beef tenderloins come peeled or unpeeled, which refers to a thick layer of fat that must be removed before cooking. Peeled beef or pork tenderloin will still have a tough membrane of silver skin that should be trimmed off before cooking, says Cook's Illustrated.
Beef or bison tenderloins can be roasted or smoked. If cut into steaks it is often served grilled or pan-seared. Some cooks will season the outside of the meat with cracked pepper or other spices, but marinating a beef tenderloin is not necessary as it doesn't need the tenderizing effects that a marinade provides. According to food writer Lori Alden, pork tenderloin, on the other hand, is often marinated before cooking.