Abstract: With the integration of a large amount of diversified renewable energy sources into the Energy Internet (EI), the complete utilization of these renewable energy sources and the power system operation face a new environment. This challenges the system's supply and demand balance and its efficient, economical, and stable operation. To adapt to this new environment, promote the real-time balance of supply and demand, achieve sustainable energy supply, ensure local energy consumption, and maintain stable economic benefits, the Energy Terminal (ET), the final energy user in the EI, has garnered widespread attention. ETs, the last link in the energy supply chain, involve various forms of energy, such as electricity, gas, cooling, and heat. They are directly related to the distribution, utilization, conversion, storage, and user interaction. These terminals are distributed across the user side and participate in the grid's energy regulation, unified scheduling, and price incentives in various forms, maintaining a crucial position within the EI. In this context, ETs are positioned based on energy consumers, producers, management platforms, and interaction nodes. A class of ET concepts is thus proposed, describing their application scenarios, definitions, and characteristics. Subsequently, based on energy market demand, energy facility planning, and energy efficiency assessment, the key technologies for implementing ETs in the EI are analyzed from five aspects: modeling, control, optimization, transaction, and planning. Finally, the future development prospects of ETs are overlooked.