What does a star do?

Could you elaborate on the multifaceted role of a star in the cosmos? Do they simply shine brightly in the night sky, or do they play a more intricate part in the workings of the universe? Are there any unique properties or behaviors that distinguish stars from other celestial bodies? Additionally, what are the mechanisms behind their ability to generate light and heat, and how do these processes contribute to the overall functioning of our galaxy and the universe at large?