A market order takes the best prices currently available until it is filled. It trades price certainty for execution certainty: you will almost always get done, and you accept whatever the book offers.
In a deep market that is barely noticeable. In a thin one it is expensive, because your order eats through several price levels to find enough size. This is why the same market order behaves very differently on a major pair than on a quiet one, and why "the price moved against me instantly" is usually a description of thin depth rather than bad luck.
Binance Academy covers this in more depth: https://www.binance.com/en/academy/glossary/market-order
Trading crypto from Dubai since 2019.
#Crypto #CryptoEducation #Binance