Gatsby is a popular open-source static site generator that enables developers to build high-performance websites and applications. Here are some of the key features of Gatsby:

1. Fast performance: Gatsby is designed to deliver fast and optimized web pages. The framework uses server-side rendering and preloading to minimize load times and improve performance. Additionally, Gatsby can be optimized for search engine optimization (SEO), which can improve the visibility and ranking of web pages.
2. Scalability: Gatsby is highly scalable and can be used to build websites and applications of any size. The framework is designed to handle large amounts of content and can be easily integrated with content management systems (CMS) such as WordPress, Drupal, and Contentful.
3. Extensibility: Gatsby includes a wide range of plugins and extensions that can be used to add functionality and customize the framework. Developers can use plugins for tasks such as image optimization, data sourcing, and styling, as well as create their own custom plugins to meet their specific needs.

Overall, Gatsby is a powerful and flexible framework that provides developers with the tools they need to build fast and scalable websites and applications. Its focus on performance, scalability, and extensibility make it a great choice for developers who want to create high-quality web experiences. Additionally, Gatsby has a supportive community and extensive documentation, making it easy for developers to get started and learn more about the framework.