The regulatory body of the securities industry. A delivery-order system used by market makers to broadcast quotes to other market makers. To some extent, it was designed to replace private telephone negotiations on stock quotes among market makers. It is similar to an ECN but does not have to comply with the SEC Limit Order Display Rule. The ability to sell stock at the inside ask price.
Ordinary investors have to sell on the bid, which is lower than the ask.
See shorting a stock. It is a similar to paper trading in that there is no actual money involved. The purpose is both to practice trading and to become familiar with the trading software. The difference in the price of the stock that appears on a quote screen at the time you place a trade and the price at which your order is filled. The greatest slippage occurs with non-direct access brokers.