Exchange rate differences. By consulting the exchange rate information published on the official website of the People's Bank of China, the difference between the buying exchange rate and the selling exchange rate is called the exchange rate difference. This spread is a very important concept in foreign exchange transactions, which refers to the difference between the buying exchange rate and the selling exchange rate when banks or foreign exchange institutions conduct foreign exchange transactions. The buying exchange rate refers to the exchange rate at which banks or foreign exchange institutions buy foreign currency from customers, and the selling exchange rate refers to the exchange rate at which banks or foreign exchange institutions sell foreign currency to customers.