Why does the Audi A7 have a mild hybrid system and what are its benefits?

I've heard that the Audi A7 has a mild hybrid system, but I'm not sure what that means or why it's important. Can someone explain?

The Audi A7's mild hybrid system combines a lithium-ion battery and electric motor with the traditional internal combustion engine, providing for improved fuel efficiency and reduced emissions. This technology also enables the engine to briefly shut off while coasting and restart smoothly, saving energy and enhancing the overall driving experience.