National Association of Securities Dealers Automated Quotation System (Nasdaq)
Nasdaq is a global intranet providing brokers and dealers with price quotations on traded, over-the-counter securities. Unlike the NYSE auction market where orders meet on a trading floor, Nasdaq orders are paired and executed on a computer network. Level I service provides the best bid and offer (BBO) in a given security without identifying the market maker. Level II service provides the BBO and identifies the market maker. Level III service allows registered market makers to compete and trade by entering their own bids and offers.