Every action, every button click, basically every input is sent to the server, and the changed dom is sent back to the client. And we're all just supposed to act like this isn't absolutely insane.
Basically you write only backend code, with all the tools available there, and a thin library makes sure to stich the user input to your backend functions and output to the front end code.
Honestly it is kinda nice.
It's extremely nice! Coming from the React and Next.js world there is very little that I miss. I prefer to obsess over tests, business logic, scale and maintainability, but the price I pay is that I am no longer able to obsess over frontend micro-interactions.
Not the right platform for every product obviously, but I am starting to believe it is a very good choice for most.