Why does the Audi A7 have a 48-volt mild hybrid system?

I've heard that the Audi A7 has a 48-volt mild hybrid system. What exactly does this mean and how does it benefit the car?

The 48-volt mild hybrid system in the Audi A7 allows for regenerative braking and engine start-stop functionality, resulting in improved fuel efficiency and reduced emissions.

Not only does the 48-volt mild hybrid system in the Audi A7 help save fuel and reduce emissions, but it also provides an extra boost of power for faster acceleration and smoother driving.