A biosimilar (akin to a generic version of a biologic) with the added distinction that it can be substituted directly for a brand name biologic because it applied (to the FDA) to become one and then passed additional tests showing swapping it wouldn’t cause any problems. All interchangeable biosimilars are biosimilars but not all biosimilars are interchangeable biosimilars. You can find what if any biosimilars and interchangeable biosimilars are approved for a biologic by searching the FDA Purple Book.