In contrast to photonic crystals, random media lack spatial symmetry but are characterized by spatial and temporal correlations in the dielectric function. This results in unique effects on light propagation through such media. We begin by deriving the transport equation for light in random media, which, under specific conditions, leads to the diffusive behavior of photons. Following this, we explore phenomena such as Anderson localization and coherent backscattering, which can be attributed to time-reversed scattering pathways and the associated interference effects of photons. Lastly, we examine the application of random media as linear optical elements capable of focusing light to subwavelength spots, introducing the concept of singular-value decomposition in this context.