Quasar evolution is the study of how quasars, which are extremely bright and distant celestial objects powered by supermassive black holes at the center of galaxies, change and evolve over time. Researchers investigate various aspects of quasar evolution, including their formation, growth, and decline, as well as their impact on the surrounding galaxy and environment. This research helps us understand the role of quasars in the evolution of galaxies and the universe as a whole.