This application is an example isomoprhic SSR application. Think Next.js, but more configurable
When users first make a request, they are served HTML. Thereafter, the client downloads a javascript bundle that makes the application act as a single-page-application, making requests to the server to obtain the props to render as needed. These client-side transitions result in the same page being rendered that would be served as HTML at that path (hence the isomorphism)
Requests are isomrphic with regards to content rendered on the page, redirect behavoir, and headers.
Only props that have changed are fetched from the server, which allows for faster response times, and eliminates unnecessary renders in the client application