### React Static is a CLI, build tool, and React NPM module that helps build progressive static sites for React. It generates progressively enhanced static websites or PWAs by producing static HTML files for each page that can act as the entry point to the progressive application. Once loaded in a browser, these pages are invisibly rehydrated with the actual React application, creating an instantaneous navigation experience for users. The build process is mainly dependent on Webpack bundling, downloading remote assets and data, and exporting routes to HTML and JSON. However, as sites grow in size and complexity, build times can become unrealistic, necessitating optimization strategies such as reducing bundle size, optimizing React templates, using multi-core machines, and implementing incremental builds.