Credit card is a micro-credit payment tool provided by banks to users. Used for post-consumption payment. It is a special card issued by banks or other financial institutions to people with good credit status. Used for shopping and spending at designated merchants or depositing and withdrawing cash at designated banking institutions. It is a special credit certificate, which can be used to pay for goods or services with high credit limit, as well as products and services with low credit rating. When the balance of the reserve account is insufficient to pay, the cardholder can overdraw the quasi-credit card within the specified credit limit, and a certain reserve can be deposited in the card as required. When we talk about credit cards, we generally refer to credit charge cards, which means only credit cards. Credit card is a special card issued by banks to units and individuals. It is a consumer credit certificate, which can be used to pay various credit loans. Credit card has many functions, and guests can pay directly by credit card. It is very convenient to withdraw cash from different places when going out for travel or business trip. Before going out, deposit a sum of cash in the local card-issuing bank and then take the card out of the destination online bank to recharge it. Moreover, the issuing bank also allows short-term overdraft within the prescribed amount. If the funds in the credit card account of the issuing bank are insufficient to pay cash, the cash can be deposited into the local bank account by bank transfer. Even if the credit card is accidentally lost, it will not cause any loss, as long as the password is not leaked. The issuance and promotion of credit cards have greatly reduced the circulation of money and cash, greatly saved the expenses of manpower, material resources and financial resources, and saved the expenses of designing, printing, transporting, storing and counting cash.