  Over the last twenty five years, holographic duality has revolutionised our
understanding of gauge theories, quantum many-body systems and also quantum
black holes. This topical issue is a collection of review articles on recent
advances in fundamentals of holographic duality and its applications with
special focus on a few areas where it is inter-disciplinary to a large measure.
The aim is to provide a sufficient background on relevant phenomenology and
other theoretical areas such as quantum information theory to researchers whose
primary expertise is in quantum fields, strings and gravity, and also the
necessary concepts and methods of holography to researchers in other fields, so
that these recent developments could be grasped and hopefully further developed
by a wider community. The topics relating to fundamental aspects include
understanding of bulk spacetime reconstruction in holography in the framework
of quantum error correction along with the spectacular advances in resolution
of the information paradoxes of quantum black holes; quantum complexity and its
fundamental role in connecting holography with quantum information theory;
theoretical and experimental advances in quantum simulators for information
mirroring and scrambling in quantum black holes, and teleportation via
wormholes; and a pedagogical review on wormholes also. The topics related to
applied holography include applications to hydrodynamic attractor and its
phenomenological implications, modelling of equation of state of QCD matter in
neutron stars, and finally estimating hadronic contribution to light-by-light
scattering for theoretical computation of the muon's $g-2$.
