Credit cards are not money. As the name implies, they give you credit: an IOU. The bank, in other words, is loaning you money when you use a credit card. You have to pay this money back within a certain time frame or you will be charged interest for the use of the money. The interest is often very high, so if you don't have the money to pay off the credit card, it it best to avoid using one. If you must borrow money, it is best to get a lower cost bank loan.
Money, in contrast, is legal tender that you get in form of metal coins and paper bills. Once you hand that over in exchange for a good, you don't have to pay anything else. There is no interest charge for paying with cash, because cash is not a loan. Cash is the best way to purchase items, though one we have moved away from in this culture because it is cumbersome to carry around cash—and puts you at risk of being robbed—whereas credit cards are easy to carry. However, they are not the same as cash.
Some eateries in New York City made the news not too long ago because they announced they would not accept cash. That was a problem on several fronts: first, a country's currency is legal tender in that country, and it is illegal not to accept it. Second, many people pointed that barring cash payments discriminates against the poor, who may not have a credit or debit card. Third, privacy advocates noted that all credit or debit card transactions are tracked and that individuals may not want every purchase they make tracked. This helps illustrate that money and credit cards are not simply interchangeable: one is loan and leaves a trail; the other, money, is simply a price paid for a good or service.