  The article reviews the physics of Anderson localization on random regular
graphs (RRG) and its connections to many-body localization (MBL) in disordered
interacting systems. Properties of eigenstate and energy level correlations in
delocalized and localized phases, as well at criticality, are discussed. In the
many-body part, models with short-range and power-law interactions are
considered, as well as the quantum-dot model representing the limit of the
"most long-range" interaction. Central themes -- which are common to the RRG
and MBL problems -- include ergodicity of the delocalized phase, localized
character of the critical point, strong finite-size effects, and fractal
scaling of eigenstate correlations in the localized phase.
