OpenAI's Generative Pre-Trained Transformer (GPT) is the revolutionary AI language model behind ChatGPT, a chatbot sandbox trained on an unprecedented quantity of human-written text and code. As a result, it has the ability to communicate and write code in response to prompts at a level never before seen. First opened to the public in late 2022, it has become the world's fastest-growing app, and the potential implications for automation, job security and the future of human society are enormous and foundational.