Best price (Market order): this order lets you buy or sell an asset instantly at market price. Its advantage is the instant execution, but it has a disadvantage in that you cannot predict the exact price at which the asset will be bought or sold.
Set price (Limit order): this lets you post a buy or sell order with a fixed price. However, it won’t execute instantly — only when the market price reaches the price you entered. Additionally, the amount you want to buy or sell is deducted from your balance and reserved in the order.