Route context is a struct type object which encapsulates the necessary information for the server from the current request context. We named it route because it’s related to the route of URL remapping. Usually it’s passed to the page handler as a unique argument. It’s supposed to provide sufficient data about the current request.
(HTTP-METHOD URL-rule (lambda (<route-context>) ...)) ;; e.g: (get "/hello" (lambda (rc) "world")) ; rc is <route-context> type