Next.js is a React framework used to build modern web applications with a focus on performance, scalability, and developer experience. Here are the main purposes and use cases for Next.js. read here more about step by step nextjs tutorials.

1. Server-Side Rendering (SSR)
Next.js allows developers to render React components on the server, generating HTML on each request. This improves SEO and reduces initial load time for dynamic web pages, as the content is visible to search engines and users more quickly.

2. Static Site Generation (SSG)
It supports building static websites, where pages are generated at build time. This approach is excellent for sites that don’t require frequent updates, offering faster load times and better scalability.

3. Hybrid Static & Dynamic Apps
Next.js enables a hybrid approach, where some pages can be statically generated while others are rendered on the server. This flexibility allows developers to optimize different parts of the app for performance or dynamic content.

4. API Routes
You can create API endpoints directly within your Next.js app without needing an external API server. This makes it easy to build backend functionality alongside the frontend.

5. Incremental Static Regeneration (ISR)
ISR allows you to regenerate static content in the background after the site is deployed, ensuring your app can be updated without rebuilding the entire site. This is useful for pages that change frequently but don’t need to be dynamic on every request.

6. Performance Optimization
Next.js optimizes performance with features like automatic image optimization, code splitting, and caching. This ensures that only the necessary assets are loaded and everything runs efficiently, resulting in faster load times.

7. SEO-Friendly
Because Next.js supports server-side rendering and static generation, it helps ensure that pages are SEO-friendly by serving fully rendered HTML to search engine crawlers. Meta tags, structured data, and custom head elements can also be managed easily.

8. File-based Routing
It uses a file-based routing system, meaning routes are automatically created based on the file structure. This makes it simpler to set up routing without the need for third-party libraries like React Router.

9. Internationalization (i18n)
Next.js has built-in support for internationalization (i18n), making it easier to build multilingual websites by automatically handling locale detection and routing.

10. Fullstack Capabilities
With Next.js, you can build full-stack applications since you can integrate backend code (like database access) with React on the frontend, eliminating the need for a separate backend framework.

11. Edge Rendering
Next.js supports edge rendering, allowing your application to be served from a CDN’s edge nodes. This improves load times and overall user experience by rendering content closer to the user's location.

12. API Integrations
It simplifies integrating third-party services (e.g., authentication, payment gateways, headless CMS) and building applications with serverless architecture using API routes and server-side code.

13. Developer Experience
Next.js enhances the developer experience with features like Hot Module Replacement (HMR), automatic code splitting, TypeScript support, and Fast Refresh, making the development process more efficient and productive.

In summary, Next.js is used to build scalable, high-performance web applications that need SSR, SSG, SEO optimization, and advanced routing with a seamless developer experience. It is highly flexible, making it suitable for both static websites and dynamic, server-rendered applications.