An LLM, or Large Language Model, like ChatGPT, is an advanced type of artificial intelligence model designed to understand, generate, and interact with human language. It is trained on vast amounts of text data to recognize patterns, understand context, and produce responses that are coherent and relevant to the given input. LLMs are used in various applications including chatbots, content generation, language translation, and more. They are characterized by their large scale, which allows them to handle a wide range of language-based tasks with a high degree of proficiency.