Cash is concrete and real foreign banknotes and coins. When customers want to transfer cash out of the country, they can do so by carrying it or remitting it. However, when the customer "remits", since the cash is in physical form, the bank must transport it abroad, and the transportation costs will be borne by the customer, which is manifested as "selling cash and buying foreign currency" (the customer sells cash and buys foreign currency). cash). It can be seen that cash cannot be converted into spot exchange of the same amount. If the cash is to be converted into spot exchange, the customer will suffer a certain loss in the amount of foreign exchange. Spot exchange is the foreign exchange on the books. When it is transferred out of the country, there is no physical transfer, it can be remitted directly, it is just a transfer on the account. When withdrawing cash in cash, since the remitting party has already borne the transportation fee, the same amount of cash can be withdrawn in cash.