A credit card is a piece of plastic that actually allows you to use a bank’s money for a short period of time.
The name itself is an indication that the bank is giving you some amount of money to use.
This amount is not a gift so you have to pay back the amount that is spent using a credit card.
The amount has to be paid back usually within 15-20 days of the end of the credit cycle of the card.
If the amount is not paid back by the due date then the interest meter would start.