A credit card is a bank-issued financial instrument with a pre-determined credit limit that allows you to conduct cashless transactions. The credit limit is set by the card issuer depending on your credit score, history, and income.
You can buy things now and pay for them later with the card. It's crucial to remember though that the amount of money you can spend with this card is limited by your credit limit. Furthermore, you must repay the money by the due date. If you are unable to do so, interest will be imposed on the monthly sum carried forward until the dues are paid in full.