What happens to a star when the hydrogen becomes helium?

When a star exhausts its hydrogen fuel in the core, nuclear fusion slows down, causing the core to contract under gravity. This increase in temperature and pressure eventually ignites helium fusion, transforming helium into heavier elements like carbon. As a result, the star expands into a red giant, altering its outer layers and ultimately leading to different outcomes based on its mass, such as shedding its outer layers or possibly becoming a supernova.