Many people may wonder, Agent seems to be not that far from LLM, so why is Agent so popular recently, and why is it not called LLM-Application or other words? This has to start with the origin of Agent, because Agent is a very old term, and can even be traced back to the remarks of Aristotle and Hume. In a philosophical sense, agent refers to an entity with the ability to act, and the word agent refers to the exercise or manifestation of this ability. In a narrow sense, agent usually refers to the manifestation of intentional action; accordingly, the word agent refers to an entity with desires, beliefs, intentions and the ability to act. It should be noted that agents include not only human individuals, but also other entities in the physical and virtual worlds. Importantly, the concept of agent involves the autonomy of individuals, giving them the ability to exercise their will, make choices and take actions, rather than passively responding to external stimuli.