What is the process of losing their outer layers causes stars to lose?

The process of losing their outer layers in stars is primarily driven by stellar winds and the nuclear fusion reactions occurring in their cores. As a star ages, it expands into a red giant and begins to shed its outer layers due to increased radiation pressure and thermal pulsations. This mass loss can lead to the formation of planetary nebulae in lower-mass stars or supernova explosions in more massive stars, ultimately influencing the star's evolution and the chemical enrichment of the surrounding space.