When you use a credit card, you're borrowing money from the card issuer and promising to pay it back later. You also promise to pay interest if you can't pay the bill in full every month. If you're having a cash flow problem and think you can repay the debt, then a credit card might be a good choice. Or if you're trying to boost your credit score, using a credit card responsibly will help you do that. With some credit cards, you also can get rewards points.
When you use your debit card, the money you spend is subtracted from your bank account. Some people prefer using a debit card so they don't have to carry around cash. Others use debit cards as a budgeting tool so they're less likely to overspend.
Another major difference involves consumer protection. When you use credit cards, you're protected by federal laws. For instance, you can dispute charges on your statement. When you use a debit card, you aren't protected by these laws.