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Level II is a trading system providing a list of all the buyers and sellers for every stock traded on the exchange, and is primarily of interest to day traders. Bids (offers from buyers) are displayed in price order (highest to lowest) and Asks (sellers) are arranged from lowest to highest price. Level II allows a stock day trader to figure out the "depth" of the market and can therefore help in deciding whether to trade or not (depth is 'size' - is the stock being investigated liquid or not?). In order to use a level II system successfully, a trader must understand the importance of each player and market maker on the screen. A direct access trading system that incorporates Level II is makes a trader's activities more likely to succeed, as it effectively 'levels the field'. If you are trading via a spread betting account, the information is of no use to you as there is really only 1 market maker - your spread betting firm.