Glossary
What is a market order?
In one sentence
A market order executes immediately at whatever price is currently available — fast, but with no control over what you actually pay.
A market order prioritises certainty of execution over certainty of price. It takes the best available offers until filled, which in a liquid market means you get roughly the price on screen.
In a thin or fast-moving market it can mean something quite different. Your order consumes each price level in turn, and the average fill can be well away from what you saw. Placing a large market order into a shallow book is one of the more reliable ways to get a bad price.
Market orders make sense when execution genuinely matters more than price, and in deep markets where the difference is negligible. For anything small, illiquid, or during a violent move, a limit order is usually the better instrument.
For example
The price you see when you press buy is a recent trade, not a promise about your fill.