You’ll have to leave a security deposit in case you incur any charges for new damage to the car, traffic fines, missing fuel, and so on.
If you return the car in the same condition, you got it with the same amount of fuel, and didn’t get any traffic or parking fines, then the supplier will release the security deposit. Otherwise, they will deduct the amount of the charges from it.
You’ll need a credit card in the main driver’s name for the supplier to hold the deposit. How much this will be is shown in the Rental Conditions of each car.