Astro is a content-first web framework built around the islands architecture: ship zero JavaScript by default, hydrate only the components that need interactivity. Created by Fred K. Schott, Astro 4.x supports React, Vue, Svelte, Solid, and Preact components in the same project, plus first-class Markdown and MDX for content-heavy sites.
Most production Astro sites are documentation, marketing pages, blogs, e-commerce frontends, and exactly the kind of site CourseFlix runs on. The framework's strength is shipping markup that scores 95+ on Lighthouse out of the box; its weakness is dynamic apps where Next.js / Remix have richer ecosystems.