A credit card is a small plastic card that allows users to make purchases and pay for them over time. The card issuer opens a revolving line of credit for the user and charges interest on any balances that are not paid off each month. Credit cards differ from debit cards, which deduct funds directly from a linked bank account, and charge cards, which require payment in full each billing cycle. While credit cards have grown popular for their convenience, issuers charge fees for late payments, exceeding the credit limit, cash advances, and other penalties to mitigate risk.