What does the Audi A1's City Emergency Braking system do?

I am interested in buying an Audi A1 and noticed it has a City Emergency Braking system. Can you explain what this feature does and how it works?

The City Emergency Braking system is designed to help prevent or minimize collisions at low speeds (below 19mph).

If the system detects a potential collision, it will first apply visual and audio warnings to alert the driver. If the driver does not react, the system will then automatically apply the brakes to help avoid the collision.