An order is what the traders (buyers and sellers) want to trade in. If a trader wants to buy digital currency, they will place a buy order. For example, if you want to buy Bitcoin (BTC) for $1 000, that is a buy order. If a trader wants to sell a digital currency, they will then place a sell order. For example, if you want to sell Bitcoin (BTC) for $1 001, that is a sell order.