Stellar evolution is the study of how stars change over time, from formation to their eventual death. It involves understanding the various stages of a star's life cycle, such as formation from a collapsing cloud of gas and dust, nuclear fusion in the core to produce energy, and eventual evolution into a red giant, planetary nebula, white dwarf, neutron star, or black hole. Stellar evolution is a key aspect of astrophysics and helps us to understand the physical processes that shape the universe.