Beef tenderloin is cut from the middle of a cow. As with all quadrupeds, the tenderloin refers to the areas along the central spine portion - which more or less hangs between the shoulder blade and hip socket. This muscle tissue does very little work, so is the most tender part of the cow. The tenderloin can either be cut for roasts or for steaks.
When left whole, the tenderloin is known as a filet or a Chateaubriand. When sliced, it forms various steaks. Those towards the loin end of the piece, when cut into slices two to three inches thick, are known as filet mignon, one of the most expensive steaks on the market.
Since it is the least stringy part of the animal, most beef dishes requiring high quality meat, such as steak tartare, are ideally made from the tenderloin.
