First of all, the credit card is the main card, and the supplementary card is a supplementary card applied for on the main card. The supplementary credit card is referred to as the supplementary card. It has a subordinate relationship with the main credit card, and the main card and The supplementary card belongs to the same account and enjoys a credit limit. All debts incurred by the holder of the supplementary card when using the credit card shall be borne by the main cardholder, and the main cardholder shall repay the card to the issuing bank. Definition of supplementary card: The supplementary card is relative to the main card. Each main cardholder who opens a credit card can apply for a supplementary card (supplementary card) for other natural persons with full capacity for civil conduct, or natural persons with limited capacity for civil conduct who are over 13 years old. If the card applicant is under 18 years old, he must obtain the consent of his legal representative).