Your router translates the Internet address space to a private address space, called a subnet, that is used to address devices in your home network. Common subnets used by router are 192.168.1.x or 192.168.0.x. By configuring port forwarding inside your router, the requests that Alice sent can find their way not only to your home router, but also onwards to your Antsle. In case you only want local access from inside your home network (shown as "You" in the diagram), you don't need any port forwarding in your router.