A credit card is a credit card that combines a savings account and a consumer account. By default, consumption is deducted from the credit card account. If you have money in your savings account, it will be automatically transferred from the savings account to the consumer account (that is, the credit account) for repayment on the last repayment date. If you have a credit account from the beginning, it will be automatically deducted from your extra money when you spend. For example, your credit card account has more deposits of 100 yuan. Then you spent 1 10 yuan, and your actual credit card account was overdrawn 10 yuan. You just need to return this 10 yuan.