This isn’t a guide, but any reverse proxy allows to to limit open ports on your network (router) by using subdomains (thisPart.website.com) to route connections to an internal port.

So you setup a rev proxy for jellyfin.website.com that points to the port that jf wants to use. So when someone connects to the subdomains, the reverse proxy is hit, and it reads your configuration for that subdomain, and since it’s now connected to your internal network (via the proxy) is routes to the port, and jf “just works”.

There’s an ssl cert involved but that’s the basic understanding. Then you can add Some Other Services at whatever.website.com and rinse and repeat. Now you can host multiple services, without exposing the open ports directly, and it’s easy for users as there is nothing “confusing” like port numbers, IP addresses, etc.