“IP” in this context means “internet protocol address”. A public IP is one that can be accessed from outside your home (what you see when you go to https://whatismyipaddress.com/). A non-public, or internal, IP is the one your router gives your computer, frequently starting with 192.168. This can be accessed by other computers on your network but not from outside your network.
ICANN doesn’t have the authority to levy a tax. I’m not sure how you would enforce a system like that.