React and Redux are popular JavaScript libraries for building complex web applications. Next.js is a framework built on top of React that adds server-side rendering and other features to the React ecosystem. Together, they form a powerful stack for building scalable and performant web applications. React provides the view layer, Redux provides a state management solution, and Next.js provides a framework for server-side rendering, automatic code splitting, and other optimizations. This stack allows for fast development and efficient rendering, which can lead to better user experiences and improved SEO.