When a customer wishes to trade currencies, they place an order which is then executed by a broker through the foreign exchange market. This process, known as order fulfillment, involves matching the customer's order with a counterparty who is willing to buy or sell the specified currency pair at the desired price. The broker, acting as an intermediary, facilitates the trade and ensures that both parties' orders are satisfied. This is a crucial step in the currency trading process and requires careful attention to market conditions and timely execution.