The cooling system is a closed loop where the antifreeze-coolant is pumped through the engine block and cylinder head.
Consequently, removing heat from the metal, before passing through a radiator.
Air flowing through the radiator removes heat from the antifreeze-coolant as it circulates. A thermostat controls the flow through the engine and the latest engines vary the cooling depending on conditions to enhance efficiency.
So, If your temperature gauge is in the red then you need to stop the car as soon as possible. First and foremost, the antifreeze-coolant level needs to be checked. Also, be very careful, as it will be under pressure and incredibly hot.
It’s not advised to open the radiator cap at this stage, but opening the hood is not a bad idea. Allow the engine to cool before attempting to top up the coolant system. It’s not advised to drive the car if the temperature cannot be controlled.