Host galaxies refer to the galaxies that contain active galactic nuclei (AGNs) or quasars. These host galaxies are typically massive, containing billions of stars, and are thought to play a key role in fueling the activity of the central supermassive black hole. Studying host galaxies can provide insight into the relationship between the black hole and its surrounding environment, as well as the mechanisms that drive the activity of the AGN. Researchers study the properties of host galaxies, such as their morphology, size, stellar populations, and gas content, to better understand the processes that govern the growth and evolution of supermassive black holes in the universe.