A credit card lets the holder pay with the issuing bank's money, up to an agreed limit, and settle up later. The formal credit card definition is a payment instrument drawing on a revolving line of credit; the everyday credit card meaning is simpler, buy now and pay at the end of the month. Every purchase creates a short-term loan, and whether that loan costs anything depends entirely on when the balance is repaid.
How do credit cards work
Statements run on a cycle. Purchases made during the cycle appear on a statement issued at the closing date, and the balance falls due roughly three weeks after that. Clear the full statement balance by the due date and, in most markets, purchases carry no interest at all. That window is the grace period, and it is the only free part of the product.
Pay less than the full balance and the grace period usually disappears. Interest is charged on the average daily balance, and new purchases start accruing from the day they are made until the account is cleared in full again.
What carrying a balance actually costs
Take a $2,000 balance on a card priced at 24% a year, roughly 2% a month. A minimum payment of 3% is $60, of which about $40 covers that month's interest. Repeat for a year with no new spending and the balance has barely moved. None of the arithmetic is hidden, it is simply back-loaded, which is why revolving card debt is the most expensive routine borrowing most households ever take on.
Who takes the risk
The issuer, twice over. It carries the credit risk that the cardholder never repays, and it pays the merchant regardless of whether that happens. It also refunds the cardholder first and argues afterward when a purchase is disputed, recovering the amount from the merchant's acquirer through the dispute flow. In several jurisdictions the issuer is jointly liable with the seller for goods bought on credit and never delivered, which is statute rather than scheme courtesy.
Why credit costs a merchant more than debit
Credit interchange is set above debit card interchange, and that gap is what funds cardholder rewards. Merchants asking what is credit card interchange actually built from will find it in the published tables of the card network, where a premium rewards or commercial card sits well above a standard consumer one.
Merchants accept the cost because credit raises what customers are willing to spend in a single order. The trade is exposure: credit carries the longest and most consumer-friendly dispute rights of the mainstream instruments, and businesses that ship late or bill on renewal feel that first. A recognizable payment descriptor and fast refunds prevent more chargebacks than any fraud tool bought after the fact.