What happens to the low mass and meduim mass stars when they run out of fuel?

When low-mass stars, like our Sun, exhaust their nuclear fuel, they expand into red giants and eventually shed their outer layers, creating a planetary nebula. The core that remains becomes a white dwarf, gradually cooling over time. Medium-mass stars also expand into red giants, but they may undergo more complex processes, including helium and carbon burning, leading to the formation of iron in their cores. Ultimately, they can explode as supernovae, leaving behind a neutron star or even a black hole, depending on their mass.