While you cannot train OpenAI models from scratch, you can fine-tune them. Fine-tuning is different from training and is available for some models, though not for chat models like gpt-3.5-turbo and gpt-4. The difference between training and fine-tuning lies in the scope and objectives of the process. Training refers to building a model from scratch, using a large dataset and training the model to understand and generate human-like text. Fine-tuning, on the other hand, is the process of adapting a pre-trained model (like ChatGPT) to perform better on specific tasks or domains by training it on a smaller, specialized dataset. OpenAI allows you to fine-tune base models like to achieve better performance in specific applications. To find out more about fine-tuning GPT models read OpenAI's docs about fine-tuning.