Market Order is an order to buy or sell a cryptocurrency at the best current price available on the market.
A market order usually ensures execution but does not guarantee a specified price.
Market orders are optimal when the primary objective is to execute the transaction immediately.
A market order is generally suitable when you check the list of orders already available and you agree with the volume that other users have but also with the price.
This is necessary because in case you have a larger amount to trade the system will automatically take all orders opened by other users but also the price set by them so that it will complete your order 100%. Therefore, the best price is not guaranteed.