We review the properties of stellar convection zones, in particular with respect to issues of relevance to helio- and astero-seismology. Convection is responsible both for establishing the one-dimensional average structure on top of which the waves are propagating and for maintaining large amplitude three-dimensional fluctuations that interact with the wave mode fluctuations. We discuss qualitative and quantitative aspects of these interactions on the background of numerical simulations of convection. We conclude that the average properties obtained from numerical simulations are quite robust and that the main uncertainties in applying these results to helio- and astero-seismology lie in evaluating the effects of the convective fluctuations on the wave propagation. One of the main structure effects is the elevation of the photosphere caused by the turbulent pressure. An important wave-convection interaction effect is the contribution of the fluctuations in the turbulent pressure to the effective gamma of the turbulent gas.