2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/14223We review basic properties of advection-dominated accretion flows (ADAFs) and their applications to astrophysical systems ranging from Galactic binary systems to galactic nuclei. A new classification scheme for low-luminosity, X-ray bright galactic nuclei is highlighted. Some outstanding unresolved issues are discussed.17 pages, a review in Astrophyscial Discs, ASP Conf. Series 160Astrophysicstext