Energy internet is a networked cyber-physical system including the production, transmission, consumption, storage and transformation devices of various primary and secondary energy sources and corresponding information, communication, control and protection devices. In the energy internet, the power grid is the core. In this paper, the key facilities in energy internet and their future development are reviewed from the following 4 aspects: energy production, transmission, conversion and storage. 4 energy carriers are investigated, i.e., power, natural gas, heating, and transportation. The distinct characteristics and technical requirements of these energy networks are analyzed. The energy router concept in electrical systems and the interfaces between electricity and other energy carriers are introduced. Besides, hybrid energy storage technologies and their development tendency under multiple energy carriers are predicted. In order to better coordinate the application of these key equipment in energy internet, the supporting technologies in the energy internet are expounded from two aspects of planning and operation. Finally, some thoughts on the development of energy internet are given.