They mean the rewards. You can get some % cash back with no annual fee. Effectively my credit card costs me nothing, comes from the same bank as my checking and savings, and gives me cash back.

the other end of this is that all of those rewards are paid for through merchant fees, which lead to higher prices at the register. it's not free money. it's a fraction of a percentage of the profit credit card companies receive in fees paid by the places you shop. i would not be surprised to learn that even with rewards points we spend more money now that those programs are commonplace.