Does freecodecamp use server side rendering with Jade? If yes, then what does it use react for?

I am new to React and I have this confusion. A clear explanation on client v/s server side rendering with react would be appreciated. Thank you.

The client sends request to the server for information. That information is then displayed in your React or w/e frontend framework you use. This saves server from using resources, processor, RAM, bandwidth, etc so it can just focus on giving you information instead of displaying it. There’s more to it but Freecodecamp I believe uses React because it’s modular, broken down into pieces that fit together. Makes maintaining the code easier.