ChatGPT is a large language model developed by OpenAI. It is an artificial intelligence program designed to understand and generate human-like language, allowing it to communicate with people in a conversational manner. ChatGPT is trained on massive amounts of text data from the internet and other sources, which enables it to answer questions, provide information, and engage in a wide range of conversational topics. It's used in various applications like chatbots, personal assistants, and other conversational interfaces.