  Recent theoretical developments on $R_D$ and $R_{D^*}$ -- discrepancies
between experimental data and the Standard Model predictions have been reported
(B anomaly) -- are reviewed. New Physics explanations for the B anomaly and
other relevant observables to obtain additional bounds on New Physics are also
summarized. This is the proceedings for the talk at CIPANP2018 which was held
on May 29 2018.
