Debit cards are linked directly to a checking account and use funds that have already been deposited, while credit cards allow purchases to be made without immediately paying and require repayment of balances over time. Debit cards provide access to cash from ATMs and require a PIN for transactions, while credit cards typically only require a signature. While debit cards avoid interest charges and do not require credit worthiness, they offer less fraud protection than credit cards and can incur overdraft fees if funds are insufficient.