ChatGPT is an advanced AI chatbot created by OpenAI. It operates using Large Language Models (LLMs), specifically the Generative Pre-trained Transformer (GPT) series. These models are deep learning neural networks trained on vast amounts of text data. ChatGPT processes natural language input to generate coherent, contextually relevant, and human-like text outputs. It stands as a prime example of Generative AI, capable of creating novel content rather than just analyzing existing data.