  This review discusses the present experimental and theoretical status of rare
flavour-changing neutral current $b$-quark decays at the begin of 2018. It
includes a discussion of the experimental situation and details of the
currently observed anomalies in measurements of flavour observables, including
lepton flavour universality. Progress on the theory side, within and beyond the
Standard Model theory is also discussed, together with potential New Physics
interpretations of the present measurements.
