Wikipedia has a clear enough explanation of Charge card, so will just reproduce here
"A charge card is a card that provides a payment method enabling the cardholder to make purchases which are paid for by the card issuer, to whom the cardholder becomes indebted. The cardholder is obligated to repay the debt to the card issuer in full by the due date, usually on a monthly basis, or be subject to late fees and restrictions on further card use.
Though the terms charge card and
credit card are sometimes used interchangeably, they are distinct protocols of financial transactions. Credit cards are revolving credit instruments that do not need to be paid in full every month. There is no late fee payable so long as the minimum payment is made at specified intervals (usually every thirty days). The balance of the account is charged interest, which my be backdated to the date of initial purchase. Charge cards are typically issued without spending limits, whereas credit cards always have a specified credit limit that the cardholder may not exceed."
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Yup... So with merchant paying 1 or 2% and they giving cash back/points etc.. the margin is comparatively very less, these are kind of baits to bring in the customer, to make them use the card in the first place... The real deal is what I told you, the interest, fees , interest on fees etc etc..