A demo ski is a used ski that comes with bindings on it. Some bindings can be adjusted to any boot size, others are fitted to a specific boot size (you can find that information under "condition". Buying used saves resources, and is one of the best ways a skier can lower their environmental footprint. Our used skis come from demo fleets and customers (like you!) through our customer trade in program.
New skis have never been skied and never seen snow. New skis often come without bindings, but others come as a "system set" and are listed with "bindings" in the product title.