The price of a stock, usually a common stock. The price is determined by the matching process executed by that stock's specialist; divided amonst a bid price and an ask price:
The "bid" is the price closest to the last transaction that buyers are willing to buy at. The "ask" is the price closest to the last transaction that sellers are willing to sell at. You can also think of them as the market price of a stock--bid being the market price if you are selling "at the market" and ask being the price if you are buying at the market. The difference between the bid price and the ask price is called the "spread." It is a fee that the market maker pockets as payment for keeping the market liquid. Generally, you will only see bid and ask prices quoted for NASDAQ stocks. On the NY and American exchanges the spread is a more uniform 1/16 to 1/8 point.