What is cylinder deactivation and how does it work in the Audi A2?

I've heard the term cylinder deactivation in relation to the Audi A2 engine but I'm not sure what it means. Can someone explain how it works and how it benefits the car's performance and efficiency?

Cylinder deactivation, also known as Active Cylinder Technology, is a process where some of the engine's cylinders are temporarily shut off while driving under light load conditions. This helps to conserve fuel consumption as fewer cylinders are being used to power the car.