Credit card companies charge merchants a fee in order to process their transactions. The more you use your card, the more money that it makes for the credit card company. So they encourage you to use your card as much as possible, and one of the ways they do that is through rewards.
Cashback is a reward program where you get a percentage of your purchases in the form of cash. It might be something like for every $100 you spend on the card, you get $1 back.
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