Experimental data on intrinsic features of the combustion wave propagation in heterogeneous reactive mixtures published during last decade have initiated development of several novel theoretical models of the process. In this paper these models are overviewed, analyzed and compared. The analysis shows that ratio of the characteristic reaction time to the time of heat transfer between particles of the mixture is a key parameter for the mode of combustion wave propagation. When the reaction time is much smaller than the time of heat exchange, the combustion occurs in so-called discrete mode; in the opposite case quasi-homogeneous combustion mode takes place. It is emphasized that the development of discrete models does not reject the quasihomogeneous approach but it rather extends the boundaries of the combustion theory. Such broad approach allows understanding of many previous and new experimental results, which could not be explained within the frames-work of classical homogeneous theory.