ChatGPT is an artificial intelligence (AI) chatbot developed by OpenAI and released in November 2022. The name "ChatGPT" combines "Chat", referring to its chatbot functionality, and "GPT", which stands for Generative Pre-trained Transformer, a type of large language model (LLM). ChatGPT is built upon OpenAI's foundational GPT models, specifically GPT-3.5 and GPT-4, and has been fine-tuned (an approach to transfer learning) for conversational applications using a combination of supervised and reinforcement learning techniques. The prototype of ChatGPT was launched on November 30, 2022, and gained attention for its detailed and articulate responses spanning various domains of knowledge. However, a notable drawback has been its tendency to confidently provide inaccurate information. In 2023, after the release of ChatGPT, OpenAI's valuation was estimated at US$29 billion. The introduction of ChatGPT has spurred competition in the field, leading to the accelerated development of Google's chatbot Bard, initially based on LaMDA and later on PaLM, as well as Meta AI's foundation model LLaMA,[citation needed] which serves as a basis for other chatbot creations. Initially, ChatGPT was based on GPT-3.5. However, a version using the newest OpenAI model, GPT-4, was released on March 14, 2023, and is currently available to paid subscribers of ChatGPT Plus on a limited basis.