The difference between logging into the Dlink router via dlinkrouter.local and the default IP of 192.168.1.1 is simply that the custom web link of www.dlinkrouter.local is much easier to use for the Dlink router access so that the necessary changes can be made on the Dlink networking device like router or modem.
http://dlinkfirmwareupdate.net/
http://dlinkfirmwareupdate.net/dlinkrouter-local/
http://dlinkfirmwareupdate.net/firmware-update-on-d-link-dir-816-wireless-ac750-dlinkrouter-local/