Limit orders are placed in the order book with a specific limit price. The limit price determines the maximum or minimum price the user wants to trade. The order will be filled if the last price reaches the limit price or is better.
A Limit order may be filled with different prices to fulfill the order amount.
Sell Limit orders will fill when the last price is equal to or greater than the limit price.
Buy Limit orders will fill when the last price is equal to or less than the limit price.
Buy/Sell Market orders are executed immediately at the best available price. This means it will take any open orders on the order book (e.g. Open Limit orders). A market order may be filled with different prices in order to fulfill the order amount.
Market orders will be executed immediately at the best available price on the market and the unfilled portion (if any) will be canceled automatically. Maker orders will always incur taker fees.
About unfilled quantity for Market Order
For placing Market Order through API, there are 2 possible ways in specifying how much to buy/sell:
With a fixed quantity (parameter quantity)
With a notional value (parameter notional)
If the Market Order is sent using “fixed quantity”, the order will be filled afterwards, and there will be a slight chance to get a tiny portion of the order left unfilled, mostly due to a volatile market condition.
Sample specification of such usage for reference: