This chapter presents the fundamentals of exoskeleton robots and their applications. A complete review of the upper and lower limb exoskeletons robots for rehabilitation, for both commercial devices and those in the advanced stage of development, is discussed. The most important characteristics of each exoskeleton and the level of development are presented according to the technology maturity level (TRL) metric proposed by NASA. In addition, it has a review of the applications of each of them according to the types of pathologies. Finally, future trends of rehabilitation robotics are discussed.