credit card sub-cards are mainly designed for children and the elderly at home. Because underage teenagers or the elderly can't apply for credit cards, this function is specially opened for the convenience of customers.

the two card numbers are different, and the main card is a normal credit card. The secondary card has the same type as the primary card, and the credit limit of the secondary card is set by the primary card holder (the maximum credit limit cannot exceed that of the primary card, which can be ). Two cards are the same account (different card numbers, but the same account). The cardholder of the main card can inquire about the consumption records of the secondary card, and the main card can repay the secondary card.

if you don't understand, please ask and hope to adopt.