Abstract: A detailed summary of random lasers in disordered gain media is presented， including recent experimental and theoretical developments. We lay particular stress on the various theoretical descriptions of random laser light as well as their differences, such as the theory of light scattering, ring optical resonators, ring waveguides and so on. Some important experiments following the development of these theories are also mentioned.Future directions for the development of random lasers are discussed, and potential applications of the ZnO random laser are also described.