It's a router at the application level. So a request comes into the multiplexer, and you have your routes: /app goes to the app controller, /faq goes to the FA

It's a router at the application level. So a request comes into the multiplexer, and you have your routes: /app goes to the app controller, /faq goes to the FAQ controller, etc. Then there's binding parameters from parts of the URL, etc. (normally you'd say "router" or "routing layer" but Go calls their router a "mux" so "mux" and "multiplexer" are the typical term for request routers in Go.)