A market order is a “buy” or “sell” order that is executed at the current market price for the selected asset. For example, if you are buying BTC using the market order feature, it will be executed at the most recent market price that is visible to you on the “buy” option.
A limit order is a “buy” or “sell” order that is executed at the price you enter for the selected asset, and this order remains open until it’s executed at the selected price or canceled.