The paper present a historical overview of the chatbot’s developments. The paper defines the chatbot as a system that seeks to mimic conversation rather than understand it. Chatbots range from simple one, just based on the pattern-matching templates, to more complex architecture, based on some sort of learning process. The paper introduces some early chatbot such as ELIZA, PARRY. And some competitions. Then the paper presents some development platform and scripting languages to build a chatbot. And introduce some tricks that chatbot can use to be more like a people, such as the chatbot can direct a conversation., Failing like a human , containing errors.The last of paper presents some future challenges. How to avoid contradictory answers?