Cavity solitons represent a class of dissipative solitons which are generated inside an optical resonator. They have attracted considerable interest in the recent years due to their possible application to optical information processing. First of all, this review chapter illustrates the physics of cavity solitons in semiconductor devices. We discuss the experiments which demonstrated cavity solitons in vertical-cavity surface-emitting lasers, both below and above threshold, and all the theory which accompanied such experiments. Those features of the experimental results, which relate to prospective applications, are highlighted. The final part of the chapter deals with the theory of the cavity soliton laser