The chapter discusses the observational evidence for Active Galactic Nucleus (AGN) feedback, which involves the interaction between the energy and radiation generated by the central black hole and the gas in the host galaxy. The feedback can terminate star formation and reduce accretion onto the black hole, thus maintaining a balance between the growth of the black hole and the mass of the host galaxy. The two primary modes of AGN feedback are the radiative or wind mode and the kinetic or radio mode. The radiative mode, which occurs when the AGN is highly luminous, involves radiation pressure and winds pushing gas out of the galaxy. The kinetic mode, which is more common in massive elliptical galaxies, involves the mechanical energy of radio-emitting jets heating the hot intracluster medium, reducing radiative cooling and star formation. The chapter also highlights the role of powerful radio outbursts in groups and subclusters, and the importance of future observations with advanced telescopes to better understand all modes of AGN feedback.The chapter discusses the observational evidence for Active Galactic Nucleus (AGN) feedback, which involves the interaction between the energy and radiation generated by the central black hole and the gas in the host galaxy. The feedback can terminate star formation and reduce accretion onto the black hole, thus maintaining a balance between the growth of the black hole and the mass of the host galaxy. The two primary modes of AGN feedback are the radiative or wind mode and the kinetic or radio mode. The radiative mode, which occurs when the AGN is highly luminous, involves radiation pressure and winds pushing gas out of the galaxy. The kinetic mode, which is more common in massive elliptical galaxies, involves the mechanical energy of radio-emitting jets heating the hot intracluster medium, reducing radiative cooling and star formation. The chapter also highlights the role of powerful radio outbursts in groups and subclusters, and the importance of future observations with advanced telescopes to better understand all modes of AGN feedback.