A line of credit allows you to make buys, usually through your bank account and then you will have to pay it back. A credit cards allows you to make buys with a credit limit.
A line of credit is an account set up with a limit established and you can write checks against it , up to the credit limit. You pay interest on any money used until it is paid back, there is no grace period, you are charged interest from date of cheque till time bank credits your payment.
Credit card gives grace period in which interest is not charged on purchases. And, if the account is received by the card company before the due date, there is no interest charged.
Interest rates, may be lower with line of credit, you should check.
Is it a good idea to pay credit card with line of credit..NO, pay off your debts, don't increase them.
Once you start borrowing to pay borrowing, you will screw it up and end up in real debt.