There are two types of trading instructions:

1. Market order: refers to a buy or sell order that is executed immediately at the current market price.

2. Price-contingent order: Investors strictly set the price at which they wish to buy or sell securities. A buy limit order instructs a broker to buy a certain number of shares if the stock price falls to or below an agreed price. In contrast, a sell limit order requires the broker to sell a certain number of shares if the stock price rises to or above an agreed-upon price. The collection of limit orders waiting to be executed is called the limit order book.

In addition, there is also an order called a stop order, which is similar to a limit order. The order will only be executed when the stock touches the price limit. For a sell stop order, the stock will be sold only when the stock price falls to a specified price. As the name suggests, this order calls for selling the stock to avoid further losses. A buy stop order requires the stock to be purchased when the stock price rises to a specified price. This type of transaction is usually accompanied by short selling to avoid potential losses caused by short positions.