A market order is defined by the purchase or sale of any asset including cryptocurrency on an exchange at the best available price. Market orders are fulfilled by both buyers and sellers who take up the trade.
Market orders are completely different than that from limit orders, where any cryptocurrency can be sold only at a specified price. Market orders are facilitated by the brokers on behalf of their investors.
Being one of the most popular types of order, they add liquidity to the market. Similarly, market orders are also cost-effective as compared to other forms of orders. The only catch is, that it can significantly affect price-sensitive traders.