What is the purpose of a lambda sensor in the Audi 80?

I recently heard about lambda sensors but I am not sure what they do in my Audi 80. Can you please explain its purpose and how it functions?

The lambda sensor, also known as an oxygen sensor, is a crucial component in your Audi 80's emission control system. It helps regulate the air-to-fuel ratio in the engine to ensure optimal performance and reduce harmful emissions.

The lambda sensor works by measuring the amount of oxygen in the exhaust gas and sending this information to the engine's control unit. This allows the engine to adjust the fuel injection to maintain a perfect air-to-fuel ratio, resulting in improved fuel efficiency and reduced pollution.