No, that’s just another hypothetical app that you’re using a reverse proxy for. I just included it to show how you can also set settings for a single subdomain/reverse proxy entry that isn’t used globally on all domains that get served. I used a hypothetical REST API that needs a CORS Header that other apps don’t need (or maybe serve themselves).

admin off disables Caddy’s admin interface (which shouldn’t be public and if you’re using config files this usually isn’t needed. So just a bit of gardening)

servers sets some general server options.

and then I just inserted several blocks that each define a reverse proxy to a different app / backend to show that you can just dump them all in a single Caddyfile. And the last example to show that you can set specific settings only for a specific subdomain instead of globally. As I set headers mostly used by REST APIs, I just called that api.example.com instead of app3.example.com.