SSR always means outputting the first html as seen from the user when the app is fully loaded and ready to be interacted with. A SPA usually starts with a minimal, blank html file and a huge JS file that mounts the DOM structure and then the user can see something. SSR does the exact same thing, but on the server. From the user perspective, SSR seems faster. From a SEO perspective, SSR is better because there's some initial content on the page.