With a credit card, you have access to a line of credit which you can spend up to a certain limit each month. Once you repay what you owe, that amount is available to you again. You are only charged interest on your borrowing if you don’t repay what you owe in full when your bill is due.
With a personal loan, you borrow a fixed amount off a lender and pay it back in monthly instalments plus interest over the term of your loan. Once you’ve repaid your loan in full, you will have cleared your debt. Interest is applied to the amount you borrow over the whole term of your loan, so you will have paid back more than you borrowed at the end of your term.