A Market Price is an order type that it's executed immediately against the best price available on the Price Limit order book. As long as there are willing sellers and buyers to trade using Price Limit to build up volume, the market will fill those orders.
For example: A market Ask (SELL) will match the best available Bids (BUY) on the Price Limit order book, and a market Bids (BUY) will match against the best available Ask (SELL) on the order book.
The price of cryptos in Market Price option displayed in either Advanced trading or Quick trade is according to the last limit price order (buy/sell) processed in the Advanced Trading. Be aware that prices for cryptocurrencies by using Market option are only estimated and not guaranteed, which means that when placing your order the rate you saw may change. If you wish to secure a certain price for your order, please use Price Limit in Advanced Trading.
Market orders are often better when rapid execution is a priority over the price at which the order executes. When placing this order, the trader prefers the trade to happen immediately at the current best price available.
¹ Please be aware that by clicking on "Buy or Sell" button when placing your order on Quick Trade, you agree that the price shown is estimated and based on the latest limit price order (buy/sell) processed in the Advanced Trading order book, the price shown may change and the estimated price is NOT guaranteed.