A default route is a special type of static route that matches any IP address that is not matched by other routes in the routing table. It's often referred to as the 'route of last resort.' The default route directs packets with destinations unknown to the router's routing table to a specified next hop address or exiting interface. By setting a default route, the router knows where to forward such packets. In contrast, a static route is configured to forward packets to a specific network or subnet, cantonization is not a valid routing concept, and a backbone route is not a standard term for a type of route but could refer to the main route of a network topology, which does not serve the function described in the scenario.