Because they are both cards you can use to buy things, people commonly confuse credit and debit cards. However, these two cards are very different.
Debit cards are tied directly to a checking account, meaning when you make a purchase, the bank deducts that amount from your checking account. You don't get charged interest or make the payment later. It all happens instantaneously, and you can't spend more than what's available in your checking account.
Inversely, credit cards are essentially loans. You are allowed to "borrow" the credit limit from the creditor who issued your card, with the understanding that you must repay the funds and you'll be charged interest for this loan. You must contact the credit card company to make payments each month to maintain a low balance.