ChatGPT is a generative artificial intelligence chatbot developed by OpenAI, built on advanced large language model technology​.It was first released in November 2022 and is based on the GPT (Generative Pre-trained Transformer) architecture, specifically fine-tuned for conversational dialogue. ChatGPT is capable of understanding user prompts and producing detailed, contextually appropriate responses in natural language. Under the hood, it leverages a transformer-based neural network with billions of parameters that has been pre-trained on vast amounts of text data and subsequently fine-tuned with human feedback to improve its ability to follow instructions and have interactive conversations​Technically, ChatGPT was trained through a combination of supervised learning and reinforcement learning from human feedback (RLHF)​.In the RLHF stage, human evaluators provided comparisons of model outputs in conversation, which were used to train a reward model; this reward model then guided a policy optimization (using methods like proximal policy optimization) to make the chatbot’s answers more helpful, correct, and aligned with user intentions. As a result, ChatGPT can answer follow-up questions, admit mistakes, challenge incorrect premises, and refuse inappropriate requests in a dialogue, making it significantly more dynamic and safe for interactive use than earlier GPT models. It has been deployed in various applications, from customer support assistants to coding helpers, and its introduction has been credited with accelerating public interest in AI due to its surprisingly human-like fluency​.It’s important to note that while ChatGPT can generate coherent and contextually relevant responses, it doesn’t have true understanding or access to real-time information (unless augmented with external tools), and it may sometimes produce incorrect or nonsensical answers (often termed “hallucinations”). OpenAI continues to refine the model, and as of 2023 ChatGPT’s underlying model has seen upgrades (e.g., GPT-4) that further improve its capabilities.