η' and η mesons with connection to anomalous glue

A review of the present understanding of η^' and η meson physics and these mesons as a probe of gluon dynamics in low-energy QCD is presented. Recent highlights include the production mechanism of η and η^' mesons in proton-nucleon collisions from threshold to high energy, the η^' effective mass shift in the nuclear medium, searches for possible η and η^' bound states in nuclei, as well as precision measurements of η decays as a probe of light-quark masses. Recent experimental data, theoretical interpretation of the different measurements, and the open questions and challenges for future investigation are discussed.