How does Next.js improve upon traditional React applications with SSR and static site generation?

For anyone using Next.js, how does it improve your React apps, especially with server-side rendering (SSR) and static site generation (SSG)? I’ve seen a lot of praise for its SEO benefits and faster performance, but I’m curious to hear about real-world scenarios where it’s made a big difference. How does it stack up compared to regular React apps?