Language played a critical role in the evolution of biological intelligence, and now artificial intelligence seems to be following a similar evolutional path. A heated discussion thread in AI is autonomous agents that can follow language instructions to carry out diverse and complex tasks in different environments. However, the concept of agent has been introduced into AI since its dawn, so what has changed recently? The most fundamental change is the capability of using language as a vehicle for both thought and communication, a trait that was unique to humans.