As you sell one currency, you are buying another. The first currency in the currency pair is known as the base currency while the second currency is known as the quote currency. 8100 units of the US Dollar. In this example, the base currency is the Euro while the quote currency is the US Dollar. For more information read more in this article about on choosing which forex pairs to trade, and which to avoid.
A trader then speculates whether the quote prices will decrease or increase and trade the currency pairs based on what you believe would be profitable. Taking a short position is just like placing a bet that the exchange rate will decrease. If the price behaves as you had predicted, you close the order with a profit. But if the price moves in the opposite direction of your speculation, then you end up making a loss. However, if a trader speculates that the exchange rate will rise, then they would buy the currency pair by placing a buy order or opening a long position.