FastChat is an AI-powered chatbot tool that allows users to chat with open large language models. The tool offers a choice of three models - Vicuna, Alpaca, and LLaMA, with Vicuna being the most performant according to the developers.

FastChat is a research preview intended for non-commercial use only, and it may generate offensive content as it only provides limited safety measures.

Therefore, it should not be used for illegal, harmful, violent, racist, or sexual purposes. Users are required to agree to the terms of use, which stipulate the limitations and data collection policy of the service.

If users encounter any inappropriate content, there is a flag button to report it to the developers.For an optimal experience, the tool is best used on desktop computers, as mobile devices may compromise its quality.

FastChat is built with Gradio and has a Github code repository that developers can use to customize and implement the tool. In summary, FastChat is an AI chatbot tool that offers users the ability to chat with open language models for research purposes.