A charge card requires you to pay the full balance every statement cycle. A credit card lets you carry a balance — at interest.

There’s no universal right number. The optimal number of credit cards depends on your credit score goals, spending habits, and ability to manage payments without missing one.

A balance transfer moves debt from a high-interest card to a new card with a 0% introductory APR — pausing interest for a set period so more of every payment goes toward the principal.

Credit cards touch all five factors that make up your FICO score — and they’re the fastest-moving lever most consumers have. How you use them (or misuse them) shapes your score more than almost any other financial product in your wallet.

A credit card grace period is the window between the close of your billing cycle and your payment due date — typically 21 to 25 days. Pay your full statement balance before the due date, and you owe zero interest on purchases.

A credit card limit is the maximum balance your issuer will allow on your account at any given time. It’s set when you open the account based on your credit score, income, existing debt, and the issuer’s risk model — and it directly controls your credit utilization ratio, the second-largest factor in your FICO score.

An authorized user is someone added to another person’s credit card account who can make purchases but bears no legal responsibility for the debt. A joint account holder is a co-owner of the account who shares equal liability for the balance and equal rights to use the card.

A hard inquiry is a formal credit check triggered when you apply for new credit — such as a credit card, loan, or mortgage — that is recorded on your credit report and can temporarily lower your score. A soft inquiry is an informal credit check for background screening, prequalification, or account reviews that does not affect your score and is not visible to other lenders.