Rob's got the right answer, but I'd like to add a bit more. There is no actual web site, www.myverizongateway.com. Verizon didn't even bother (or have the good sense to?) to buy the domain. If you do a who-is search on the domain myverizongateway.com you will see it's owned by some cyber-squatter in China who wants $3,000 to sell it (presumably to Verizon).
The router has been programmed to watch for a request to myverizongateway.com (coming from the LAN - that is, equipment inside your house). When it sees one, the router returns the web site built into the router for setup and maintenance. It is the same as just typing in the IP address of the router as Rob said. You never actually make a request over the Internet; it's all done on your internal LAN connections, so there's no need to secure it.
My setup: 75/75 Mbps; Linux router (2x 1Gbps ports) + iptables; Netgear Orbi x 2