schizanon, In the beginning #websites were static files.
Then websites were generated dynamically on a server with a language like #PHP or #Ruby.
But when we wanted to do complex #frontend behaviors we would need to generate #html in the same way as those #backend languages, which was awkward.
So, we used #reactJS #fullstack to render "Single Page Apps" (#SPA) in the browser and on the server using "Server-Side Rendering" (#SSR).