An overview of the interactions between waves and particles in plasmas is given. Interest is focused on cases where special particle populations, like energetic particle tails, interact with waves. The two basic, but inter-related, mechanisms through which waves and particles can exchange energy, resonance and stochastization are briefly illustrated. The basic non-collisional interaction mechanisms and their description through quasilinear theory are reviewed. The present state of modelling and comparison with experiments in fusion plasmas is addressed. With respect to astrophysical plasmas, three topics are examined: (i) the generation of cosmic rays, (ii) the heating and fast particle generation in the solar corona and (iii) the whistler wave generation in the magnetosphere.