What is the Purpose of the Audi A2 Auxiliary Water Pump?

I've noticed that my Audi A2 has an auxiliary water pump, but I'm not sure why. What is the purpose of this pump and how does it work?

The Audi A2 auxiliary water pump is responsible for ensuring that the engine maintains its optimal operating temperature. It works by circulating coolant throughout the engine and heating system, helping to control the temperature of the engine and prevent overheating.

In addition to regulating the engine temperature, another important function of the auxiliary water pump is to help with the defrosting and dehumidifying of the windshield. By circulating warm coolant through the heater matrix, the pump helps to quickly defrost and demist the windshield, improving visibility for the driver.