What is "bordelaise sauce"

Bordelaise sauce is a classic French sauce named after the Bordeaux region of France, which is famous for its wine. The sauce is made with dry red wine, bone marrow, butter, shallots and sauce demi-glace. Sauce marchand de vins ("wine-merchant's sauce") is a similar designation. Traditionally, bordelaise sauce is served with grilled beef or steak, though it can also be served with other meats that pair well with red wine demi-glace based sauces.