Ah.... just looked at my notes and it confirms you, Modem IS a router but has no hardware firewall. OK so that's straightened out.
Well the manufacturer says there is a firewall.
Anyway, I am soon to try to insert a wireless router into my network, but that reall may not be relevant to what I'm trying to figure out.
What anonymity does it give me to toggle between "make this IP public" and " make this IP private" if I can go to WHAT'S MY IP website and I am identified?
Also, how is the modem setting my lappy NIC card address if I don't touch the lappy?
Have you accessed your device using a browser?
Can you not see what options are present there?
When your PC uses a public IP then the PC is on the internet directly, with nothing in between.
That means that your security is completely dependent on the settings in your PC.
When your PC uses a private IP your PC is not directly on the internet, but has the modem/router device connected between the PC and the internet.
What this means is that anyone attempting to break into your PC would first have to get through the modem/router before reaching the PC ....... if private IP is selected.
If public IP is selected they would be attacking your PC directly, with nothing to slow them down.
'Whats my IP' ..... reports the public IP of your connection. If you have selected public IP then that is the IP of your PC, if you have selected private IP then that is the IP of your modem/router. To do some extra reading search for 'bridge mode' in routers.
Most PCs are set up to receive an IP address dynamically. Thus they can change.
I advise most strongly that you get much more familiar with the device you have, and how it works and gets secured, before adding in another device to the mix.