Chatbots work by using natural language processing (NLP) to understand and respond to user input. The input is passed through a series of algorithms and rules that determine the appropriate response. Some chatbots are pre-programmed with a set of rules and responses, while others use machine learning to improve their understanding of language over time. The output of the chatbot is then typically returned to the user in the form of text or speech. Some chatbot are also integrated with other services like search or actions.