Over the past few years, interest and research in wireless power transmission (WPT) have been rapidly incrementing, and as an effect, this is a remarkable technology in many electronic devices, electric vehicles and medical devices. However, most of the applications have been limited to very close distances because of efficiency concerns. In spite of the fact that the inductive power transfer technique is becoming relatively mature, it has not shown near-field results more than few meters away transmission. This review is focused on the two fundamental aspects: the power efficiency and transmission distance in WPT systems. Introducing the principles and the boundaries, scientific articles will be reviewed and discussed in terms of their methods and respective challenges. This paper also shows more important results in efficiency and distance obtained, clearly explaining the theory behind and obstacles to overcome. Furthermore, new issues have been raised including safety and foreign object detection. Moreover, an overlook in other aspects and latest research studies for this technology will be given.