So in what way does if differ from traditional MVC? In MVC, the final output is HTML strings. Easy example: supposed you have an array of Posts in your controller, and a HTML template. The final result will be the combination of both of them. But when the HTML strings get sent to browser, you lose the array !!! It's gone. The client never receives an actual array, just DOM nodes.
In Front-end framework SSR (NextJS or NuxtJS), what you work with is a component. A component can have data (an array), and the data is pushed (serialize) as-is to browsers. On the browser, you won't ever have to work with low level DOM nodes. You continue to see the component and data in its original form. This is the biggest win of SSR that is easily overlooked.