A "gas rebate" is a discount or refund that you receive when you purchase gasoline. It helps you save money by giving you some of the money you spent on gas back to you. Full definition
Many issuers of gas rebate credit cards charge an annual fee, so account for that when figuring how much you will actually save. (cardrates.com)
Essentially, with a branded gas rebate card, you can expect some decent savings on on - brand gas purchases, but negligible awards on most other things. (creditcards.com)
That's exactly what gas rebate credit cards do. (cardrates.com)