The ChatGPT model (gpt-35-turbo) is a language model designed for conversational interfaces and the model behaves differently than previous GPT-3 models. Previous models were text-in and text-out, meaning they accepted a prompt string and returned a completion to append to the prompt. However, the ChatGPT model is conversation-in and message-out. The model expects a prompt string formatted in a specific chat-like transcript format, and returns a completion that represents a model-written message in the chat. While the prompt format was designed specifically for multi-turn conversations, you'll find it can also work well for non-chat scenarios too.
The ChatGPT model can be used with the same completion API that you use for other models like text-davinci-002, but it requires a unique prompt format known as Chat Markup Language (ChatML). It's important to use the new prompt format to get the best results. Without the right prompts, the model tends to be verbose and provides less useful responses.
The following code snippet shows the most basic way to use the ChatGPT model. We also have a UI driven experience that you can learn about in the ChatGPT Quickstart.