Statement balance
Everything owed on a credit card the day the billing cycle closed — a frozen snapshot, and the number the due date and grace period refer to.
The statement balance is a snapshot: everything owed on a credit card as of the day the billing cycle closed. It is frozen. The due date printed on the bill and the minimum payment both refer to this specific number.
Paying the statement balance in full by the due date is the standard move. On cards with a grace period, doing so means no interest is charged on purchases — and it keeps the grace period in place for the next cycle. Charges made after the statement closed become part of next month's statement, and they will also be interest-free if that one is paid in full.
Paying less than the statement balance but at least the minimum keeps the account current, with no late fee. But the unpaid remainder starts accruing interest, and the grace period is lost, so new purchases begin accruing from the day they post as well.
Plumb is financial education, not financial, investment, tax, or legal advice.