All terms
Market order (Market-Order)
An order without a price limit, executed as fast as possible at the next available price.
With a market order (in German also 'billigst' when buying or 'bestens' when selling) you set no price. The order is executed immediately at the next price the market offers.
This is convenient and usually unproblematic for large, heavily traded stocks during trading hours.
It gets risky with thinly traded stocks, right after the market opens, or in hectic markets. Example: you see a price of 20 euros, but your market order fills at 20.80 euros because the price moved within seconds or the spread was wide.