While both of these cuts are boneless, and the names sound similar, they are very different and come from different parts of a pig. Tenderloins are long thin cylindrical pieces of meat that are very tender and can be cooked over high heat for a short time. Pork loins, on the other hand, are thicker, not as juicy or tender, and require cooking at low temperatures for longer. In general, because they require very different cooking methods and cooking times, they cannot be substituted for each other in recipes.