GPT-3 (Generative Pre-trained Transformer 3) is a state-of-the-art language processing AI model developed by OpenAI. "ChatGPT" refers to using GPT-3 as a conversational AI, where it can generate human-like responses to text inputs. The model was trained on a large corpus of diverse text data, allowing it to generate responses on a wide range of topics and generate text that is highly coherent and relevant to the input prompt. This makes it well suited for applications such as customer service chatbots, language translation, text completion, and other NLP tasks.