Types of orders in Securities market

Brokers will accept instructions of various types concerning the condition under which a security is to be purchased or sold. Some of the procedures are institutionalized; others are simply agreements between the investor and his or her account executive .
By far the most common procedure is that used for a market order.The broker is instructed to buy or sell a stated number of securities at the best available price or prices (as low as possible for a purchase, as high as possible for a sale). it is incumbent on the broker in such a situation to act on a "best efforts" basis to get the best possible deal in time.
In most cases there is fairly good information concerning the likely price at which a market order might be executed. if this is unacceptable, a limit order may be placed instead. Both a quantity and an acceptable price are specified. The broker is to purchase or sell the stated number of shares only at the indicated price or better (higher for a sale, lower for a purchase). If a limit order cannot be executed immediately, it is usually kept by the broker or placed by the broker on the books of another broker to be executed as soon as the requisite price can be obtained .
Some limit orders are day orders-canceled if not executed by the end of the day they are placed. However, an investor may specify that an order be considered good-till-canceled (GTC) or that it be canceled immediately if not executed (this is termed a fill-or-kill[FOK]order).