Not sure how many middle schoolers you've talked to recently, but they're quite tech savvy. They're all used to google docs, tik tok, bereal, and whatever else they're using.

I'd be surprised if they didn't know what a server is. It's become common lexicon to say "Oh that website's servers are down".

Maybe bring up that time Roblox's servers were down for 72 hours or whatever.

But yeah so, your browser sends a request to the website's servers.

The servers run code (just instructions written so that a computer can understand) to complete that request.