How does APIcast routes the API requests to the appropriate API service?

Issue

• How does APIcast routes the API requests to the appropriate API service?
• We make an API call, these calls are being mapped to the correct Product, but I'm wondering if there's documentation on how this is done? My current understanding is that first it will check the host (ie. apicast-server-url.com:portnumber) against various Products and retrieve the ones that match. Then it will compare your request (ie. /get/request) against the various Mapping Rules set up in the Products that matched the host. If any Product has a mapping rule set up it will use that one. If it can't find any, it will then search the Mapping Rules set up in the Backends of the Products that match the host. Is this an accurate understanding? Do the Authentication details factor in at all?