What they mean is that, with a normal React SPA, the html content sent to the client will be little more than something like `<div id="react-app"></div>`. Afte

What they mean is that, with a normal React SPA, the html content sent to the client will be little more than something like `<div id="react-app"></div>`. After the JavaScript loads, react hooks into this div and starts filling it with the html it generates for your app. With SSR, that div will be populated with html when it’s downloaded - this is the html that was rendered by the server. When the page is first rendered it will look like your app, but it’s totally static html. The JavaScript has to load and react has to take over managing the html within that div before any of the interactive content (think: button click handlers on so on) will be functional.