A market order is a buy or sell order to be executed immediately at current market prices. With this order type the focus is on the number of tokens bought or sold and does not allow the user to select the price.
A market order can fill more than one order on the order book.
Here is an example:
In selling 500 ZRX the first 97 will be sold at 0.000915 and the rest will be filled by the next order down in the order book at 0.0009145. These two orders are highlighted in the order book to the right.
Be cautious when placing market orders on thinly traded order books.
In the example below, a market sell of more than 106.9~ tokens would lead to an unfavorable trade rate. The second order on the order book is significantly lower than the first.