New to trading, want to know what determines a match of 2 orders in the market. Think of an example here: A stock is trading at $10, there’s an order willing to sell at $15. If I place an order to buy at $15 now, does this trade get executed right away ? Or do I need to wait till the price gradually moves into $15 before it can be executed This is to suppose that somebody is willing to overpay (demand), and there's someone want to sell at that exact price (supply). But if the current trading quote differs from that, Can this trade take place ?