It is now widely accepted that every galaxy with a bulge weighing over
about a billion solar masses hosts a supermassive black hole (SMBH) at
its center. While SMBHs are quiescent most of the time, they are
occasionally awakened from sleep by falling material and start to roar.
Such an activated SMBH is believed to manifest itself as active galactic
nucleus (AGN), an extremely tiny and luminous source found in some
galactic centers. AGNs have long been studied as an important
constituent of the Universe, but on top of that, we are starting to
realize that they might have impacted the evolution of the host galaxies
in an irreparable way. I will start the talk with a general review of
SMBHs, AGNs, and their interrelation with the host galaxies, and then
will focus on one of the hottest topics of the field, AGN-driven
winds/outflows observed in the host galaxies which might be closely
related to the so-called co-evolution of galaxies and SMBHs.