Integrable dispersionless PDEs arising as commutation condition of pairs of vector fields

We review some results about the theory of integrable dispersionless PDEs arising as commutation condition of pairs of one-parameter families of vector fields, developed by the authors during the last years. We review, in particular, the formal aspects of a novel Inverse Spectral Transform including, as inverse problem, a nonlinear Riemann - Hilbert (NRH) problem, allowing one i) to solve the Cauchy problem for the target PDE; ii) to construct classes of RH spectral data for which the NRH problem is exactly solvable; iii) to construct the longtime behavior of the solutions of such PDE; iv) to establish if a localized initial datum breaks at finite time. We also comment on the existence of recursion operators and Backl\"und - Darboux transformations for integrable dispersionless PDEs.