The HTTP route for a service is the publicly-accessible directory path that maps to the root of your service.
For example, if you set the HTTP route for a service to be /myservice1, and your app is serving on the domain mydomain1.com, then requests for mydomain1.com/myservice1 will be routed to this service for a response. This allows you to use different services that are exposed at different subdirectories, each with their own configuration, capacity, and scaling characteristics.
If your backend service requires the full HTTP request path preserved, set the preserve_path_prefix annotation to true in the App Spec.