What is the use of a oxygen sensor?

[Michael]

Hi,
   I want to know that many car's provide comes with  oxygen sensor. But i didn't know what is oxygen sensor and what does it do. Please tell me about this. 

[anand mohan]

Hi Michael,
                An oxygen sensor measures the amount of unburned oxygen in the exhaust system left after combustion in the engine's cylinders. Based on the amount of Oxygen present, the sensor generates a voltage which is read by the engine's fuel management system. Too much residual O2 in the exhaust, and the car's computer releases more fuel for the next combustion cycle; too little O2, and the opposite happens.

thankyou,