Tell us about yourself!
I think you are correct, for the most part? The ip on the router, for folk using a regular home Internet provider the routers ip will be assigned via the providers dhcp server and it is subject to change. So you would need an outside facing static ip so it would not change or use a service to point to whatever the dhcp assigned ip changes to. I was setting up ip cameras at my house and I think the issue would be similar.